Could I get a little guide on

Could I get a little guide telling me how to create new user groups or "ranks" who have access to certain parts of the forum please?

n admin panel
Users & Groups>Groups>Group Administration
Create a new group.

Fill in the details as you want,
Group members color, select the color which you want to be displayed.
Check color group members.
Group status: Select Closed group
Permission to send PM Mailings : According to your choice

Then hit save.
Now
----
1. Administration Panel
2. General tab
3. Categories and forums
4. Click on a forum
5. Click Permissions
6. Check Advanced
7. For that specific group: view the forum, etc...change it accordingly.
Do it for all the forums.

Hope this helps.

Thanks that is going to help so much when I set up my forum