You need a program called unlgp to be able to unrar lgp-archives (FF7- gamefiles), or to be able to repack them again. Download UNLGP. Learn how to use it through it's readme-file and then do the following to install my addons. Readme in folder. 1. Back up your "char.lgp" found in your FF7/data/field folder. Then unpack it using UNLGP and rename that folder "char". You can unrar an lgp-archive by doubleclicking on the lgp-file after you have installed the program unlgp. Put all the field-model files in your new "char"-folder. Aeriths textures are now compatible! When you have decided who you want to add you should create a new lgp-file. You can do this easy by clicking on "swift" at the same time while you are right-clicking on the folder. Click on "create lgp" as it will be such an option. The file will then be created and you should wait until it finishes. Make sure the file is named char.lgp. Reppeat the same process for the rest in menu_us.lgp and battle.lgp. Tifa's Bootleg add-on.
I've replaced Elena's field model and battle model with Tifa Lockhearth, using the PRB model in the field (because i got tired of trying to make the Kaldarasha model look good and decided for the easier solution) and Kaldarasha's model in battle (took many hours).
Also, i'm in the process to replace Tifa with Elena of the Turks - battle model already ready since last year thanks to Grimmy who HEX-edited it so that the NPC model can be used as a playable character - field model also finished by me during the night.