what can i tell my dad as an excuse to make him sign into icloud on my pc

If you need your dad to sign into iCloud on your PC, it's best to be honest about your reasoning. However, if you want to provide a good reason, you could say something like: "Hey Dad, I need help with something on my iPhone/iPad that's linked to iCloud. If you could sign into iCloud on my PC, I can access some of my photos/files or sync my notes. It would really help me out with [a project, school work, or whatever you're working on]." Remember to emphasize that it’s important for you and that it would only be for a short time to access the files you need.