To restore the database you usually do it via your hosts control panel.
(Should be the same place where you backed it up!)
However, make sure you have tried de-activating all plugins you have on your site before doing anything else to see if that fixes the issue. Then you may be able to narrow it down to it being a plugin issue and not a WordPress one.
I tried this to no avail, but some people seem to be having these redirection issues because of incompatible plugins.