At first go to hosting panel/cpanel then go to file manager and then public html folder.
After that, go to qa-include folder and then go to qa-theme-base.php file edit it to remove "powerd by" and save.
You can remove "snow theme by q2a market" by following this step..
public html > qa-theme> SnowFlat > qa-theme.php . Then edit and remove the line and save.