Change new site domain name

I am a student, new to the online Website techs. As a wealthy affiliate starter,and tempororaly can t afford to buy a web site, I was
offered couple new web sites hosted under www.ads-software.com to start with. Wrongly the domain names I did chosen was not relevant to the title of the site. I learned after that the domain name should be the same as the site name, to be effective and get ranked.
If it doable, would sbdy direct me to where or how I can change domain Name of my site?
Thanks

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