I can see you added a profile for your dad. The next step is to add profiles for his parents. If you don't know who they are, you can ask a living relative or you can try to find out some other way.
One way is to use familysearch.org.
If you are in the united states, you would go onto family search and enter your dads name. Since he was born in the 1930's you would look for the 1940 census.
I always use a whole decade for the birth year so enter his birthdate at 1930 to 1940. You should find him and his siblings in that census. It is easier with practice and you use the same formula on different websites.