How do u rep someone thank u

Click on the user you would like to give rep to and toy should see a button which says "Rate." Click that and give the amount of rep you would like to give. Once done, click submit and it should be added to the users rep.
 
Go to their profile and look for this:

Click on 'Rate' and give that person how much rep you want to give them, in your case, being -1, 0 or +1 since you're only a donator.
 
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