[Support request] Ability to edit Login Form?

I’m setting up a website for an astronomy society with a membership who pay via a different route than via the website (MemberMojo). I do however want to have content that only approved society members can see. At the login page it has links to ‘Join Us’, which would link to our page about joining details for the society, but I want to modify the login page to add a link to the registration page to register to get on the website.

Does anyone know if I can add that Register link to the login page or modify the login page at all, in fact? Ideally it would say ‘Request Access (for existing society members)’ then link to the registration form.

Thanks