Where does current go in these circuits?
It is implied that the 9 V source has its negative end connected to ground.  Current therefore flows out the positive end of the 9 V source, into the circuit, out the circuit's ground connection, and back into the negative end of the 9 V source.

Added

As Dave Tweed pointed out in a comment, and I didn't notice ealier, the second circuit uses a positive ground.  In that case, current flows out the positive end of the 9 V supply into the circuit ground, thru the circuit to the -9V connection, and back into the negative input of the 9 V source.

The common thread in both cases is that ground is implied as the 0 V reference for all other voltages that don't explicitly specify a reference.  Both the "+9v DC" point in the top circuit and the "-9v" point in the bottom circuit are therefore relative to ground.  Since they are labeled as supply points, it is assumed that a power supply is connected between these points and ground.