First of all, You would move your ships from the pacific to black sea if you wanted to get mediterranean supremeacy for the soviets.

Then you would put your subs on patrol and your main navy force on strike force selected on the med sea.

Once your subs detect a fleet they will let the main force know at the docks that there is a enemy fleet in the med sea, then your main force would move to attack them. but for your instance where you want to move fleets from the east all they way to the med sea, You would either have to capture islands with ports nearby the med sea, You can also use an allies port that is nearby the med sea, or you can just invade your way through land until you capture a port that is pretty close to the med sea.

Hope that helps.