Hey Jake,
Wool shrinks under these combined conditions: heat, water, and agitation. Therefore, soak your wool sweater for a half day in a basin of cold water with a bit of very gentle soap, like Ivory. Gently squeeze the sweater with your hands, without twisting it. After you squeeze it, let it soak again for an hour or so. Then. Drain the water while supporting the sweater, don't allow it to stretch. Fill the basin with cold rinse water, and squeeze it gently. Do this several times, changing the rinse water till it runs clear. Then, lift your sweater out of the basin, lay it n a heavy bath towel, and roll it up in the towel. Avoid wringing it. Repeat this with anther bath towel until it's not dripping wet. To dry your sweater, lay tin another dry towel in the floor. Turn as it dries. It may take a few days to dry, depending upon how heavy it is. Good luck!