First you figure out how many grams of sulfur has been used.
2.080g - 1.659g = 0.421g of S used
Now change all of your grams to mols.
1.659g of Cu / 63.546g/mol = 0.02611mol of Cu
0.421g of S / 32.065g/mol = 0.01313 mol of S
From this you can see that S has less so we divide both numbers by the number of moles of S so we can get a ratio of S to Cu.
0.01313/0.01313 = 1 for S
0.02611/0.01313 = 2 for Cu
So the empirical formula would be Cu2S or copper sulfide.