[HELP] I have recently started managing the content.

[paulbaker]

Kariba = badged version of CMS Made Simple (from the login screen, at least).

Yes you might well need full admin access.

Look in:
Content -> Global Content Blocks for header
or Layout -> Templates for page templates

Perhaps Content -> Gallery for slider
or Content -> Showtime

One of the lovely things about CMSMS is there is always >1 way of doing something, so it's not always possible to say how they something in the front end is done in the back end.