Generally those sort of changes are better handled by editing the theme directly. Since each theme has different code and layout that makes it very hard for an app to know what to change, and how it should be done.
I am not sure how far down the path you've gone with the current theme but there are others that might have this feature built in.
Please provide your website link and password to access it.
The merchant doesn't need to email you a password. If you need to see something to be able to help consider asking them to post the storefront (not admin!) password here. Partners are not encouraged to solicit emails from merchants so if you want to help, do it here.