If you need to have some users that are able to deal with pages (create, modify, delete, approve) and files (load photos and so on), the easyst way is to create a group

C5 is a little bit confusing in this becouse you need to specify what they can see AND what they can do.
I'm running on C5 ver 8.2.1

Following a short guide to setup a simple Editor group

0) select Dashboard\members\user groups: Add a group (blue button) and give it a name... do not alter the "parent group section"

1) select Dashboard\sitemap\full sitemap  so you have on the left of the page the full menu tree (dont forget to act on "options" button to see all items: site pages and system pages).

2) on left tree click Dashboard, permissions --> check Editor group

3) on left tree doubleclick on Dashboard, click Files node, permissions --> check Editor group on "Who can view this page?"
then do the same (or check if done) on each child page of "Files" node

4) on left tree doubleclick on Dashboard, click "SiteMap" node, permissions --> check Editor group on "Who can view this page?"
then do the same (or check if done) on each child page of "Sitemap" node

.. now you can hide the other menu entries (or check), as Express or so on, doing as above for each entry but unchecking Editor group

5) on left tree click on Drafts, click on permissions: "who can view this page" --> check Editor group + "who can edit this page" --> check Editor group

Now you will act on the right tree !

6) go into System & Setting\files\File Manager Permissions: add editor group for each one except "View Files" (dont forget to save each time and at the end

7) go into System & Setting\Permission & Access\Task Permission: add Editor group in "Access Sitemap" and "View Site in Maintenance Mode"

8) go into System & Setting\Permission & Access\Site Access: check Editor group in "Edit access" section
 
9) go into "Pages & Themes"\"page types": click on "Permissions", then add Editor group in "Add Pages of This Type"  

---------- DONE (this was a basic example)  --------------

C5 is much more sophisticated if you try "System & Setting"\Permission & Access\Advanced permissions: it works great but refer to documentation to see how to do it.