To install Homie & Follower Icons, put "follower_heads.xtbl" "homies.xtbl" "interface-backend.cpeg_pc" "interface-backend.gpeg_pc" and "ui_bms_04.xtbl" files in root folder with game exe. 
For Steam users, You can right-click the game in Steam > Manage > Browse Local Files to get to it quickly.

It's recommended to keep the original .7z file for ease of uninstallation later (referring to files).

Have fun and take care!