Putting a custom modpack on your server is very easy and can be done by following steps below:
Stop your server
connect via FTP to your server guide to setup FTP can be found here
Remove all previous vanilla files
Download the modpack files of the modpack you want to your computer, and get them ready:Generally, modpack files come like this after you unzip them:
1: This is the main server jar. It will be named something like that, or forge-something, or with the modpack name. You will need to rename this file to custom.jar
2 & 4: These .bat and .sh files are used to launch the server when running it yourself, and not with a host. They can be deleted. There is an exception for some modpacks if you see a file called FTBInstall.sh and FTBInstall.bat. See below.
3: Usually there will be a file called minecraft_server.XXXX.jar you want to leave this file alone.
After you rename the main server .jar file and delete any files that are not needed you should end up with something like this:
Modpacks containing FTBInstall.sh and FTBInstall.bat files:
If you see FTBInstall.sh or FTBInstall.bat files you will need to execute one of them. .bat is for Windows, and .sh is for Macs and Linux.
You will need to extract the zip onto your local machine and run the sh or bat files depending on your operating system. This will generate another important jar file
After running one of the two FTBInstall files you will see that another file appeared:
Now you can rename the main server .jar (FTBServer-1.7.10-1408.jar like we did above for section 1) to custom.jar, so you end up with something like this:
This ^^^ is the files you need to upload to your server via FTP
In the Game Panel click on commandline manager. Then click select on custom jar. In the JAR dropdown select custom.jar and click the apply button. This will tell your server to load the custom.jar file .jar you had renamed in the previous steps.
Start your server
If you get stuck we can get the modpack on your server for you:
VERY IMPORTANT: PLEASE MAKE SURE YOUR SERVER.PROPERTIES PORT AND IP MATCH THE CONNECTION INFO ON YOUR SERVER IN THE CONTROL PANEL.