Bus to wire in quartus
Just connect it up directly with a wire (you will see a little blob appear to show it is connected). Then, name the bus something like name[msb..lsb], and then name the wire name[whichbit]. That will tell Quartus to connect them because they both have the same name and tell it which bit it should connect to. You will get errors if you choose a whichbit which is less or more than the msb and lsb of the bus.

Better still, don't bother with the schematic and wire it all up in a Verilog (or VHDL) file.