You don't put it on the surface of the star; you orbit at a distance far enough away to maintain a reasonable temperature. Current solar panels are about 300 grams per square meter, but there are much opaquer materials than silicon, so you can probably get down to a hundredth of that. A sphere at the radius of Earth's orbit would be 2.8e23 square meters and thus at 300 grams per square meter 8.4e22 kg. Earth's moon masses 7.3e22 kg, while Jupiter masses 1.90e27 kg. So there's at least five orders of magnitude more raw material than you need.

If you happened to live in a planetary system without adequate gas giants, you could probably find some way to scoop mass off the surface of your star or capture it from coronal mass ejections, then use fusion to transmute it into the materials you need. Even Sun is 1.90e30 kg, and it's rather small as stars go.