Creating a mod.pack using PFM in 4 easy steps

For a deeper explanation on how the system works, see Daniu's Modding Primer.
Pack File Manager (PFM) can be found here[www.twcenter.net]
For assistance with your mod, be sure to visit the Mod Workshop[www.twcenter.net] at TWC

Step 1: Add a new personal mod in PFM
File -> MyMods -> New. Enter the name and location that you want to store it. (IMPORTANT: Do not put any spaces in this name or the official mod manager will not install your mod when it comes time to use it)
-- When you have a mod selected under MyMods, extracted files are automatically added to the specified mod pack

Step 2: Import required files into your mod
The next step after naming and locating your mod, is to choose what it contains. Open the relevant official pack (more than likely: data_rome2.pack) and PFM will pop out a new window for you to choose the files from. Double click on the files you want to include in your mod, and hit OK when you are done.

Step 3: Make your changes

Step 4: Install your mod
UPDATE
With the addition of the official mod manager, manually editing the user.script file and/or PFM's install function no longer works as a reliable method of installing a mod.

To install personal mods (not uploaded to steam workshop), copy your mod into the data directory as normal, then tick the box in the top left hand corner of the mod in the Rome 2 launcher mod manager. To use a mod from the steam workshop, subscribe to it in the workshop and after it has downloaded it will show up in the mod manager. Enable the mod by ticking the little box again