1- On a PC with Windows AIK installed, open CMD as Administrator.
2- Run the following commands from the root of C:\ or whichever drive you will be mounting the drive on. If you use something other than C:\ make sure to modify the commands as listed.
mkdir Offline
DISM /Mount-Wim /WimFile:"<location of WIM file>" /index:1 /MountDir:C:\Offline
**The Image is now mounted in the C:\Offline folder.
3- Locate the drivers to be injected and copy them to a convenient location. In this example mine are in C:\Drivers, then run the following
DISM /Image:C:\Offline /Add-Driver /Driver:C:\Drivers /Recurse
**The drivers will now be injected into the image.
4- Now we need to unmount and commit the changes to the image.
DISM /Unmount-Wim /MountDir:C:\Offline /Commit
**The image has now been unmounted, and saved to the original Boot.wim file.