Apparently, behind the handlebars.
It's the chrome cap in the oil bag, right under your right leg when sitting on the bike.
The 883 Sportster takes just under 3 quarts of oil
what type of oil for a 1993 Harley Sportster 883
Sae20W50
20/50
The dipstick on a Harley-Davidson Sportster motorcycle is read by noting the position of the oil in relation to the markings. The oil should be between the full and add marks.
20w50 motorcycle oil
Under the motor
SAE 20w50 100% synthetic oil.
To add engine oil to a Sportster 883, locate the oil filler cap, which is typically found on the right side of the engine near the rear. Remove the cap, and use a funnel to pour the appropriate type of oil into the engine. Be sure to check the oil level using the dipstick or sight glass, if equipped, to ensure it's within the recommended range. Always consult your owner's manual for specific oil type and capacity guidelines.
Should be right at 3 quarts
Three
HD makes a weight of oil they call "Sport-Trans" that is made for use in the Sportster primary. Or, you can use any 30W non-detergent oil.