It's pretty easy. Post a request to have your user name changed in this forum - https://forums.qrz.com/index.php?forums/add-my-call-sign-to-qrz-database-helpers-forum.121/ and then follow the DX Helper's instructions.
@S53DW Please go here and enter the mandatory information so that your callsign can be added to the database. https://forums.qrz.com/index.php?threads/please-add-my-callsign-s53dw.911386/