Welcome to TM
Run the engine to scavenge the oil back to the tank. Turn the engine off and let things settle for a couple of minutes and then check the oil level with the dipstick in the cap in your case, or the two level indicator plates inside the tank on later cars. Don't check the level a few hours or more after the engine has run or you may get a false level as the oil can drain back from the tank into the sump.
If it is overfull, drain some oil from the tank or suck it out with a syringe. It's not good to run overfull, particularly with early oil tanks that have been known to split.
