Changing domain name in cpanel(vistapanel)

When made my site with my host i got a https://dotcomsolutions.byethost3.com/ domain. Later i found that u can get a free domain without that .byethost3 stuff. So i did that. Parked dotcomsolutions.ga on top of my existing domain.
Then i found out that parked domains are bad for SEO.

Can i just change the https://dotcomsolutions.byethost3.com/ to dotcomsolutions.ga

I cant seem to be able to find a way how.

Any suggestions or explanations regarding the topic are welcome.