EAGLE schematic capture and board layout problems
U$1 has a TAB on that back that is probably a heatsink. Check to see if it is ground-connected, high-voltage, or floating. I'm assuming its your voltage regulator. Make a big polygon pour around this tab for heat sinking. From experience, these can heat up a lot. The warning EAGLE is telling you is that the IC symbol is listed as a power input and wants either a ground symbol or a power symbol to be connected to this pin. It appears to be floating in your schematic. If the TAB is internally connected to ground, then add a connection to the ground pin and the warning will go away.

Generally, its always a good idea to stick a wire on an IC pin, give it a name, and then connect it to a test pin that you can put on your board later for debugging. This can greatly help you down the road and also make your unconnected warnings go away.