You can normally take the ethernet cord from the modem and put it in the wireless router in the ethernet port marked internet
Addsionally you can set up the router's wireless connection as a secured network. Look at your manual you got with your router if it's new for instructions.
Otherwise most routers are 192.168.1.1 type it into your browser and the default password and user name is normally admin for the name and admin for the password or password for the password. If it's a spacific type tell me and i can tell you what the default passwords are on the router.