Download the Minecraft server jar for the appropriate Minecraft version from mcversions.net.
Make a directory for the server, and put the server jar you downloaded there.
Launch the server .jar. You need Java installed for this, of course. The command line for that should be:
java -jar server.jar
The server will fail to start. A new file, eula.txt, has appeared in the server directory. Edit it with a text editor and set the eula entry so it looks like this:
eula=true
Install the latest Forge for the appropriate version of Minecraft matching the pack. You can find it at files.minecraftforge.net. Select the right version, download the Forge .jar installer, and copy it into your server directory. Then, run it as you did with the server.jar. If you are on a server without a GUI available, or just wish to do it this way, you may run it like this to install without the GUI (substituting in the correct filename for the version of Forge you just downloaded, this is just an example):
java -jar forge-1.10.2-12.18.2.2179-installer.jar --installServer
You now have a working version of a Forge enabled Minecraft server. You should make a startup script. Mine uses this line to start the server (you may need to increase the -Xmx3584M option depending on how many people will use the server):
java -Xms1024M -Xmx3584M -jar -XX:+DisableExplicitGC -XX:+UseConcMarkSweepGC -XX:MaxTenuringThreshold=15 -XX:MaxGCPauseMillis=30 -XX:-UseGCOverheadLimit -XX:+UseBiasedLocking -XX:SurvivorRatio=8 -XX:TargetSurvivorRatio=90 -XX:+UseCompressedOops -XX:+OptimizeStringConcat -XX:+AggressiveOpts -XX:ReservedCodeCacheSize=2048m -XX:+UseCodeCacheFlushing -XX:SoftRefLRUPolicyMSPerMB=20000 forge-1.10.2-12.18.2.2179-universal.jar nogui
You now only need to install the mod pack. Install the client as you normally would and take note of where it is installed.
Now, from that installed Minecraft instance with the pack installed, likely in a minecraft directory, copy these directories and their contents to the server directory:
config/ scripts/ mods/
That's it, the server and client files for the pack are actually the same. Steps 1 to 6 are normal Minecraft server installation procedures. It just required those three directories and their contents. So, use that startup script to start it, and that should be that. Enjoy!