The ground and vcc comes from the top left power connector (note the 5V and GND rails at the bottom are the ones you see in the image above, and are connected to A1-A4:
You have several errors. The first one is you need to add a power flag to the GND net.
I would strongly advise use the GND power symbol instead of tracing the ground wire all across the schematic, this will make it much easier to read and less prone to mistakes!
The second thing I notice is on CP1, it needs junctions dots to connect to the wire, otherwise it is not connected.
The small square on the end of a wire or pin disappears when it is properly connected. The two places circled in red need to have junction dots to connect.
The small squares highlighted in blue show two wires that overlap but do not connect. In KiCad overlapping wires are not connected, they must meet end to end. When they do, the small squares will disappear.
The ERC report is often confusing, because where the error is reported is often not where the error is! You need to trace along the net to see where it didn’t connect.
I try to avoid wires overlapping symbols, text or even other wires if possible. In this case you can simplify the drawing a lot by using the GND power symbol.