I need to write minutes and an agenda for a meeting, don't even know where to start?

There are many ways to do it; see some here.

For meetings I take minutes for, I simply head each section with the same name as the sections of the Agenda, note the time each section started, then take plenty of notes.

After it's all done I then consolidate the notes from each section down to 3-4 concise sentences summarizing them.

I also then consolidate those 3-4 sentences into one sentence; which is what I read out loud at the next meeting.

If you don't have to read them to the group, then the last step is not needed.