Since you are looking for a guide for a .rar file, here are a few technical tips:

The game uses a hidden point system to track your affinity with each sister.

"...even though we're twins, we can't be together forever, can we?" "...but what will happen if I distance myself so suddenly?" "...try to catch her." "...refuse to help." "I should sneak up from behind and hug her."

The game runs on the Ren'Py engine, meaning it is compatible with Windows, Mac, and Linux.

Every choice you make grants points to either Ichika or Futaba.

If the game won't launch, ensure you have extracted all files from the archive into a single folder, as Ren'Py games require specific game and renpy subfolders to function. Sisterly Bliss ~Don't Let Mom Find Out~ | vndb

Use a tool like 7-Zip or WinRAR to extract the contents.