The mod installation guide
Important note: some anti-virus programs can regard the .exe file as a virus. It's because the program injects the data into other files, i.e. replaces old textures with new ones.
2) Run the file: Texmod.exe
3) Click the folder icon on the left beside the text "click left button to select an application".
4) Find and select the AssassinsCreed_Dx9.exe (it should be in your Assassin Creed's main game folder)
5) Click the small folder icon right above the red 'X'.
6) Load appropriate .tpf files. You may choose from: BlackNinja.tpf, BlackNinjaEyes.tpf, Damascus_night.tpf, Ezio Auditore De Firenze.tpf, Red_Livery_Assassine_Version_1.tpf, Red_Livery_Assassine_Version_2.tpf, Jerusalem_night.tpf (that can be found in Jerusalem at night package).
Important note: you can choose only one texture for your Assassin, either:
BlackNinja.tpf + BlackNinjaEyes.tpf
Ezio Auditore De Firenze.tpf
To each you can add Damascus_night.tpf to have Damascus at night and/or Jerusalem_night.tpf to have Jerusalem at night.
7) Click Run.
8) Choose the 6th memory (the assassination of Robert de Sablé) and have fun!
Note: BlackNinjaEyes.tpf, Damascus_night.tpf and Jerusalem_night.tpf work also in other memories.
PS This mod is only for PC version of Assassin's Creed.