If you have bought a subscription for broadband (landline or mobile) and it included a router this information is often written down on the back of the router.
SSID is followed by the name of your network and PASSWORD is followed by the password that was set when the unit was delivered.
If it does not work, one reason could be that the password (or SSID if you can't find it when trying to connect) have been changed when the equipment was installed. Ask that person or company that helped you to find out if that has been done.
If a router was not included with the subscription and bought (or given) separately the password is often set at setup of the router and is not found on the back of the router. The SSID could also have been customized. Ask the person or company that helped you install this equipment.