changed domain but kept same website/content, cant login to wordpress

I used to run philanthropackr.com but recently registered a new domain, planesandpassports.com. www.remarpro.com is installed in my hosting with Hostgator, I simply wanted to keep the same website and content but change the name. Now I can’t login to my www.remarpro.com account since philanthropackr.com is no longer a hosted domain.

Can someone tell me how I can login to wordpress with my new domain and still access the old site with the same content? the new domain reflects my old website but I am not able to login with wordpress.