Use one hot wire (12v) either right to battery, or to a wire that gets 12v when key is in on position. (You can use the blue wire) Lets use the blue for argument sake. Okay, so you splice a wire to the blue, then this wire goes to the center post of switch, use one of the end post and attach a wire to go to 85 (one side of relay coil) 86 goes to ground..
this is what happens.
turn bike on, 12v is now on blue wire and to wire you spliced in.
this goes to switch (switch in off position to start)
turn switch to on.
this gives 12v to relay coil (other side of coil is to ground so it completes the circuit)
it powers up and....closes the internal contacts of relay
now the 12v from battery which is connected to relay (post 30)
and the internal contact closed to post 87 the 12v goes to the accessory you want power.
set switch to off, that accessory gets no power.
post 30 and 87 are inter changeable, you can connect the battery to either 30 or 87. doesn't make a difference, once the relay is energized the relay internal contacts close and connect 30 and 87 together.