Assuming by refilling the oil, you mean that you wish to perform an oil change. In that case all you need to do is follow these instructions
1. Unbolt drain plug and let the oil flow out until it stops.
2. Re-install the plug. (make it snug, not too tight)
3. Locate and unscrew the oil filter
4. Check the filter gasket to make sure it isn't stuck to the engine, if it is remove it as this will cause the filter to leak
5. Lube the new filters gasket with CLEAN engine oil and install. (again, snug it)
6. Fill the engine with oil up to the max line on the dipstick, and run it for about one minute. (this allows the oil filter to be filled.) Make sure it isn't leaking oil.
7. Check the dipstick again and add more oil accordingly.
The 318ci (5.2) requires 5 quarts of 10w30 oil and a Fram PH16 or similar oil filter
Good Luck with your Ram!