You need to read this before you do anything else: Your first model is going to suck. Bad. And that's okay.
If you have never painted anything before you start on your models, they are going to be beyond terrible. Suck a bowling ball through a garden hose terrible.
AND THAT'S OKAY.
If you have never done this before, your first models are going to look this bad:
Yes, this a Warhammer 40k model. I couldn't find any badly painted BattleTech figures. Honest.
That's because you don't have the experience and the knowledge to paint them as beautiful as you see others paint theirs. Like in any endeavor, you have to try at it and fail several times before you find something that is pleasing to you. There are many levels of painters. You will not be terrible for long. The level of quality you achieve all depends on the level of time and effort you want to put into painting. The only painter you have to be better than is the painter you were yesterday.
I once knew a guy who pro-painted and customized Games Workshop models for people. His models looked like they could do the Indian in the Cupboard thing. He once showed me a Thunderhawk Gunship that he painted. Mind you, this thing is about 5 feel long. I took a look in the cockpit, I could almost make out what was on the displays and read the gauges. Remember, this has been his job for years. 8-10 hours a day, 5-6 days a week.
I am a mediocre painter, I know that and I accept it. I don't want to spend days painting a single model, I would much rather play with them. I paint them to an okay standard then move on.
I am writing this so you don't get hung up and lose heart and motivation. Think of everything you have in your life, every achievement you have accomplished. You were royally terrible at it, in the beginning. Then you got better. So you will here.
Believe it or not, you can actually strip the paint off your models and try again. So, try again.