Terminal 1 has concourses A/Z, B and C which you can see on level 2 and 3 of FRA airport map.
In these you will be guided through immigation (passport & visa check) when not arriving from inner Schengen zone.
After this you are in a secure zone of the concourse which you have to leave: follow signs "Exit" and/or "Baggage claim" to public zone of Terminal 1. Without checked luggage your cousin could pick you up there (level 2 after leaving concourse).
With checked luggage follow signs "Baggage claim"; escalators and stairs will bring you down to level 1 (arrival level) where the luggage belts are. Signs or an electronic board will show you on which belt the baggage from your flight is provided. After collecting your luggage you will leave this zone through the customs area - choose "nothing to declare" (if so) and just walk through. You will come into the arrival area in which cousins, hosts, family and friends welcome and pick-up their arriving passengers.
If you agreed to meet your cousin at a different place go there now. Tip: in every terminal there are meeting points.
Hope this helps.