There is some overlap between part 1 and 2 but that is OK.
A multi-meter allows you to test different stuff, so it will have a lot of ‘settings’ and will have the slimmest of manuals. It will have ohms, AC and DC settings. You don’t care about AC cause all cars, motorbikes, and scooters use DC. You will have several DC settings. Since your scoot uses a 12 volt battery you will set the m/m at 12 or 20 or something like that, just as long as you set it at 12 or the next larger setting the m/m will read accurately.
On the DC setting your m/m is going to tell you whether electrons are going out of your battery, down the wiring to the taillight bulb, then back to the other side (ground) of the battery. Electrons love to run around in circles or loops, it makes them happy.
So you can take your turn signal light apart, remove the bulb, and put the m/m on the two wires there and tell whether the electrons are running around ready to light your bulb. You already know how to test the bulb with a battery and some wires.
What confuses most people is when they take apart a turn light and they can only find one wire !@^@#%@# Holy Crap. Trust me here, in that case I guarantee that the negative (-) side of your battery will have a big, black wire on it that is firmly attached to the scooter frame. You go look at your battery and I’ll wait right here. 
I told ya. So attach the red lead from the m/m to the turn signal wire and the black lead onto the frame. Find a bare spot on the frame because electrons don’t like to run thru paint. Yes, there is always electrons running around in your frame and your motor every time you ride. Works just as good as wires.
Helpful Hint. Practice this stuff on working components. You won’t learn it til you do it. Reading and watching videos ain’t learning skill, it’s learning potential facts.
