Hey, Tuck. Welcome to DC :-)
I used to use these when I was a server at the local officers' club, when we had buffets. You just light the gel in the tin with a match. If it seems to be putting out too much heat, you can partially cover the opening with the lid. I wouldn't take the fuel out of the tin.
Keep the lid - when you're done with the fire, put the lid back on and it will extinguish the fire. If I'm looking at the same item you bought - Amazon.com: Cooking Fuel - Gel: Home & Garden
- the product description says it's reusable, as long as there is still fuel in the tin. HTH.