Using an app without giving acces to mac

To keep your Apple ID account secure, see the following Apple articles:

Manage and use your Apple ID

Manage and use your Apple ID – Apple Support (UK)

If you think your Apple ID has been compromised

If you think your Apple ID has been compromised - Apple Support

Delete suspicious content from your devices

Delete suspicious content from your devices – Apple Support (UK)

See who has access to your device or accounts

See who has access to your iPhone or iPad – Apple Support (UK)

Never jailbroken your iPhone.

Change your Apple ID password. 

Create a strong password for your Apple ID, It is best if your password consists of eight or more characters and include upper and lowercase letters, and at least one number. You can also add extra characters and punctuation marks to make your password even stronger. 

Never provide your password, passcode, security questions, verification codes, recovery key or any other account security details to anyone else. Apple will never ask you for this information.

Then see this Apple article: What to do after you change your Apple ID or password

What to do after you change your Apple ID or password - Apple Support