Wiring a fluorescent T8 fixture to a standard plug
The extra holes in the connector are for wire chaining the fixture to the next fixture.  One pair goes to power, the other pair to the next fixture.

You can cut off the connector and strip the two wires (black and white) and connect them directly to the cord with wire twist connectors.  These are color coded for the total size of wires in them.  Yours plus a cord is likely to be the smallest (blue).



Black goes to black and white to white.
Be sure to use a three prong cord with a ground wire, like this:



Secure the green wire to the fixture's metal with a screw (maybe one already in place), or cut the end of the wire, strip it, and use a twist connector to tie it to a ground wire in the fixture.
The clamp is a great idea if the edge of the hole in the fixture is sharp.