On each side near the front of the engine, at the mounting plate area, there should be a plastic standpipe with a black dome vent cap. The standpipe portion can be unscrewed (usually by hand) to look down inside to see the oil level. If you do not see oil within 1/4 inch of the bottom of the hole, that means it is low.
If they do not unscrew, it will be tricky to get a wrench in at the base of them to break them loose. Hopefully they do not give you problems.
You can use a long metal flex funnel and some 20W-50 engine oil to top it off or use the Cub Cadet hydrostatic oil.
Make sure the O-ring at the bottom of the tube is good or replace it. Screw each tube back lightly hand tight.
After that run it back and forth a few times and see how it acts. It may still make a little noise, but it will quiet down eventually. Take it out a put it to work to see how it does.
I have realized that actual service manuals for this design are non-existent, or they are buried deep in the archives of Cub Cadet where I have not found them yet.
Much of what I have learned on mine is through trial and error, but it is a strong running machine that borders a commercial grade zero turn. I picked mine up from a customer who was just tired of the little thing adding up from his neglect of the machine.
Question: How many hours are on your newly acquired machine?