How or where do you add oil to chain and sprocket for a case 1840 skid steer?

The oil level/fill plug is located between the tires low on the body. It's a plug that takes an Allen wrench to remove. Park on level surface remove plug. When full the oil is at the bottom of the plug hole. Capacity 6 quarts per side SAE 10W-30 engine oil. Oil change interval 500 hours. Drain plug location rear bottom. Drain and flush with solvent is recommended.