Install:

Install the folder to "mods/update/x64/dlcpacks/" with OpenIV.
Go to "mods/update/update.rpf/common/data/" and edit DLCLIST.XML file, adding a new line for the new Add-On.

How to use it:
Now, you can drag & drop the wheels models files into "FOLDERNAME_mods.rpf" file of your Add-On. 
Also, don't forget to add the wheels textures in x64e.rpf (vehshare.ytd file) and x64w.rpf (vehshare.ytd file). It should be said
on the readme of the wheels packs you download from GTA5-Mods.com site. 

TheyThey'll be loaded automatically by the game when started. 
This way you don't need to edit any "x64.rpf" (except x64e.rpf and x64w.rpf) file to your "mods" folder to replace textures, 
saving a lot of GB :)

Enjoy!