So my friend gave me his old dirtbike.

So this would be my first official dirtbike that I “own” my buddy of many years offed it on me as he isn’t very mechanically inclined and wants a new bike but needs the space. So the bike is a 2000/20002/2001, somewhere in there ktm 400 sx (says it’s a full on race bike) I know about cars and engines and stuff but I’ve never had or have worked on dirt bikes, the bikes been sitting for a few years I guess. Where should k start and what needs to be done? Drain all fluids? Replace carburetor? Radiator? Plugs and wires? Starter? Can anyone help me with this thanks