Toward the bottom of each problem set is a section entitled How to Submit. Follow the instructions therein to submit your problem sets, and within a few minutes, you should see your scores in CS50.me! You may re-submit work as many times as you'd like; we will record your most recent submission's score.
If you started CS50x before 2018, know that scores from CS50x 2017 have been imported into CS50.me. In order to view them, you must first link your edX account at CS50.me/account! Your scores should be viewable shortly thereafter.