Powering the Multimeter
The skinny red and black wires power the screen. Once you put the black wire into ground and the red wire into 5V, then the screen should turn on.
Once you have that, the yellow wire will measure voltage at where you touch the metal end.
The thick Red and Black wires are wired in series to whatever you want to measure current of.
After you power up the device, it will show 0, 0.
In order to test voltage, you need to touch the yellow wire to something that would have volts. In this picture I put it on the + breadboard rail. The rail was being supplied by the 5V.
On the breadboard I put a 100 ohm resistor. To measure the current through the resistor, I connected one side to the + breadboard rail and then connected the other to the - rail by jumping it with the two thick wires on the meter. That way current travels through it to be measured.
The unit for resistance is called the Ohm, after its namesake. The symbol used to represent it is the Greek letter omega. It was first used because someone thought omega's first symbol sounds a lot like how you pronounce Ohm's name.
"I am the Alpha and the Omega"
(Koiné Greek: "ἐγώ εἰμι τὸ Ἄλφα καὶ τὸ Ὦ"
I represents current because Ampere was French. He called current "intensite du courant" which starts with I.