Theme not carrying over to admin login.

Hi, brand new to punbb, had a few issues but got them sorted with the treads here, but having an issue with the theme I chose 'flat emerald', theme works fine as regular user, but when I use the admin login it reverts to oxygen, is this a feature of punbb or is this a bug in the 'flat emerald' theme, I have very basic knowledge of php or coding in general so any solution would have to be step-by-step or a simple fix.

Thanks for any help.