To modify user permissions, go to the left side menu and click on "Edit Users". Select the user, you want to edit by simply clicking on the name field.
Go to the section "Other user permissions". Here you can set additional permissions that the selected user should have. Most importantly, you can choose "Allow access to web directories" and "Allow access to databases". Items in the left box are all available items where no access is granted. Items in the right box are directories/databases where access were granted. To move items left to right or right to left, simply click on them. When you set everything as you desire, click "Save" in the end.
In the example below, the user gets access to the parent website directories only and access to the underlining database.
