Make sure to allow part to cool to room temperature. There is a transition temp where the metal will act a little like clay instead of a rigid metal, and you risk warping it if you try cleaning up the part before it's fully cool.
Once it's cooled, you can use a hammer to knock out the sprue/well and clippers snip off any flashing or vent artifacts. Although the inner ring where the vents connected with the sprue doesn't need to be perfectly clean and sanded for this component to function, you should inspect it to make sure the vents broke off cleanly and file it to shape up those edges.
Remember recycle all your casting scraps back into the skillet. They will re-melt just like the original ingot.
Check the fit between castings once you have a couple of copies. Check for errors like warping or squashed geometry due to too much weight. Take notes on what's working for your setup so it's easy to dial in to a perfect casting.