How can I see who’s using my information

I am not sure how you can see if anyone is using it for sure. But, for safety, see these security related documents:

If you think your Apple ID has been compromised https://support.apple.com/en-us/HT204145

iCloud security overview https://support.apple.com/en-us/HT202303

Security and your Apple ID https://support.apple.com/en-us/HT201303

Ways to keep your information safe on Mac If you think your Apple ID has been compromised https://support.apple.com/en-us/HT204145

iCloud security overviewhttps://support.apple.com/en-us/HT202303

Security and your Apple ID https://support.apple.com/en-us/HT201303

Ways to keep your information safe on Mac https://support.apple.com/en-gb/guide/mac-help/mh11402/mac

Why do you think someone id using your information? More information would help.