Scooterotica

I have just bought an Acewell digital speedo and in the wiring diagram it has two 12v DC feeds one permanent(for memory) and one switched(on and off).My question is how can I switch it or have I got to add a seperate switch and remember to turn it on n off all the time?Anyone else fitted one?,these are the ones used by the bloke in Scootering last year who seems to have disappeared and forced me to do my own.Thanks