I bought my very first meter tester but I don't know how to properly use.?

I bought a multitester MT-1210 I read the instructions but I don't know how to use. I want to measure the voltage of a laptop power supply. I have really no idea what I'm doing. I'm too scared in case if I damage anything. If anyone can help me out I would be really grateful. Thanks for those who answer please don't respond to anything horrible or nasty. I'm just a novice at these things. Someone has to start somewhere right?