If your internet is decent bandwidth I'd let it finish downloading.
If it's going to take days...
I'm just guessing because I don't have the Disc. If you go to "Computer" and open the "DvD Drive - Sims 4". Right Click - Open (you can try Autorun too).
Likely there is a Setup.exe or something to that affect on the disc. Run it.
The game will still update patches from a full disc install but the size would be much much smaller than the full game.
