If you have access to the Admin Module then you can add access to the other modules by doing the following:
- Click on the Setup tab.
- Click on Getting Started
- Click on Users.
- From there click on your username (or the username you want to change).
- In the popup, check the modules you want to give this user access to
- Then click the Save button.
Note: If you don't have access to the Admin Module then you will need to contact your system administrator who does have access to that module so they can add access for you.