Preparing Minecraft Modpacks: ATLauncher Files
Preparing ATLauncher modpacks is extremely easy, as their launcher has a feature that will produce server packs automatically from a modpack.
The jar files (both Minecraft and Forge), libraries, mods and any other necessary files are produced automatically during this process. The only thing needed is the ATLauncher itself, which can be downloaded from https://www.atlauncher.com/downloads.
Start up ATLauncher
Start up the launcher and sign in. Then, on the right side, click on "Packs" 
Select the Modpack
On the following screen, find the modpack you want to make server files from, by either using the search bar at top or scrolling on the right side. For this example we will be using the modpack "Sevtech: Ages". This is a modpack we already have in our One Click Installer, we are simply using it as an example.
Create Server and Select Version
Once you located the correct modpack, click the "create server" button. 
This will cause a popup window to appear in which you choose the version to install. The most current version of the modpack will appear automatically in the window, since most people will be looking to update to the latest version. If you need an older version of a modpack click on the dropdown list and select an older version.
Click on the "Install" button to continue. Occasionally you will see a popup window with a message from the Developers, often thanking you for installing the modpack, or inviting you to join their discord channel. Click on that to close it and continue with the installation.
"Select Recommended" Window
Occasionally as you install server files for an ATLauncher modpack, a popup window appear that asks you if you want to install optional mods along with the modpack. This pop up window does not appear on all modpacks. We recommend always selecting the "select recommended" button as majority of ATLauncher modpacks will need those mods. If you do choose to install other optional mods, simply click on the mods and a check mark appears. Then, click the "install" button. You will need to tell anyone who wants to connect to the server that they will need to select these same optional mods when they install the modpack on their client. 
Wait for Files to Download
Progress bars will appear, and the necessary files will being to download. Wait for that process to finish. ATLauncher will popup a message letting you know when that has finished.
Zip, Upload, and Test
Navigate to the folder where ATLauncher was installed on your computer, and open the folder. Inside you will see the files and folders used by ATLauncher. Look for a folder called "Servers" and open it. Inside you will see a folder for each server that has been created. You can also navigate to the modpack on ATLauncher in the "servers" section and click on the "open folder" button. In our example, open the folder for Sevtech Ages. Inside the folder "SevTechAges" will be all the files needed for the server pack.
Open that folder, and inside are the files for the server!
If you haven't created an instance for Minecraft yet, go ahead and do that now. Not sure how? Not to worry, we have a quick guide you can check out here: Instances Guide
In the File Manager, click on the "apply" button beside "select all" at the bottom, then "delete". The file manager should be completely empty now.
In the main folder of the modpack on your PC, select all the files. Right click on them and zip them up. We prefer to use 7-Zip but you can use whichever zipping tool you prefer.
Upload that zip file to your server. That can be done by clicking the "upload" button in your file manager, dragging and dropping the file directly into the file manager, or via FTP.
FTP is generally the best way to upload files, especially large ones. FTP breaks the file up into small portions and sends each portion one at a time. It keeps tracks of what's been sent, checks it off a list when it gets to the other ends okay, and will resend if one gets lost. It also double-checks the integrity of what it sends, and will resend if any are corrupted. Here is a link to our guide on how to use FTP: Basic FTP Tutorial
Once uploaded to the server, select the zip file and click on the "unzip" button that appears. This should place all of your files into your main directory.
Head over to the "Java Settings" page on your panel. Under the "JAR" section, select the drop-down menu and choose the Forge jar file. Make sure you click the save button!
Finally, turn the server on! If all the steps were followed, then it should load up the modpack and go online! You can follow the startup process in the Console.