Assuming you are asking how to fill a tilt and trim fluid reservoir for an outboard motor:
Locate the oil fill cap/tube. It is typically located on the side of the engine near the bottom.
If there is no dipstick, unscrew the cap/tube and peer inside. The fluid level should be at or slightly below the bottom of the tube. If it's not, add oil until it reaches that point.
Replace the cap/tube and screw it on tightly. Wipe up any spilled oil immediately; oil can damage rubber parts on your engine.