1. Get your new user to create an account here: http://panel.offensiveservers.nl/index.php?r=site/register
2. Once they have created an account, make sure you know their username they used to sign up.
3. Now login with your Multicraft control panel account
4. On the left hand side, click "Advanced" then "Users".
5. Under Username heading, there is a white box.
6. Enter the username of the new user in there and press the enter button to search.
7. Next to the users account you can select the role to the FTP and control panel.
To change the FTP, change the first pull down box under the FTP access / FTP username. You can either select "Read Only" which means they can only read the files and not edit. "Full access" means they can edit, download, create, upload all the files.
To change if the user can have access to the control panel, you can change the Permissions under the "Role" heading. If you want to give someone full access, you can select "Administrator", if you want to limit their actions you can do "Moderator". To change their permissions, if you click the "Advanced" tab on Multicraft then click "Commands", you can create or edit commands to allow to certain users.