You need a graphic card to play smoothly and run ENBs (Just how do you play GTA without a graphic card anyway?)
Kins, you can go to Settings, Advanced Settings, Display and make your resolution higher
1280 x 720 is HD. If you have a better PC you can go upto 1920.
If you have a wooden PC like me, Im afraid there is no good way to run the game in HD as your graphic card doesn't support, either that or you will fry your PC.