If you haven't done anything yet at your store (haven't spent time adding numerous products etc.), then "deleting" your store with the old/wrong domain and creating a new store (to set the newly purchased/or correct domain) will be the easiest solution.
Deleting the store and creating it again will only take 15 minutes and you can easily do it at your end.
To delete your store, please log in to your SaleHoo Account and access the SaleHoo Stores product.
The Delete tab is on the left part of the page, right above the FAQ tab.
Clicking on this Delete tab will erase the current store in your account.
Once deleted (takes 15 minutes), when you get back to the same page/refresh, you will see the part where it asks you to create your store (which before doing so you will be asked to fill in your domain name.) At that stage you put in the new domain name which you intend to use.
Again, this step is advised if you haven't listed numerous products in your store yet. Otherwise you will need to back up your file first.
If you are still having any difficulty, give me permission and I'll delete it for you, then set the new store with the new domain name.