When first logged in to the router, the below screen will appear. All custom configuration options can be found on the menu options of the left of this screen. 

It is recommended you change the Admin password to prevent unauthorised access.

Enter a new Username (or enter admin to remain as default username) 

Old Password (default) = RB(Followed by the last 6 digits of the MAC address with colons removed)

New Password – enter password of your choice