Without realizing what I did I removed the old manual thermostat, and paid no attention to the wires locations on the thermostat before doing so .so I'm stuck with two yellows one red one blue one green and a black wire that's not been used ?
How do I determine which wire goes where?

Best I can offer is I need you to provide the model # of the thermostat, and follow the wires back to the furnace, and provide as much detail as possible where the wires go. Take photos if at all possible and attach on your post. Pic of stat is good also.

Your luck, the wires should be of a certain color code, and your set has two possible substitutions.

What type of system do you have? Heat pump? Gas ? Electric?

Really need more info to help.

Are the yellow wires yellow, or is one white? If so, this may be fairly easy to sort out. Yellow to Y, white to W, etc. Otherwise you are going to have to give us more info.

Usually there is a 24 volt AC transformer in the furnace with the secondary winding connected to a red wire running to the thermostat and a blue wire, common, to the gas valve, A/C relay, and fan relay. From the thermostat there will be white wire to the gas valve, yellow to the A/C, and green to the fan. The thermostat is wired to switch the power from the red to the white, yellow, and green as needed with the blue completing the circuit. Most thermostats and furnaces have the contacts labeled R, B or C, W, Y, and G for the corresponding wire colors. It may be wired to have the A/C control wires return to the furnace and its controls and then a second wire goes to the A/C unit. Internal wiring may replace the green wire if the thermostat does not give you the option of fan only or continuous fan. Digital or programmable thermostats may need the blue wire connected to them.