Technique I have a camera and I dont know how to use it xD

It's actually not bad.

There are some things that you can safely allow
your camera to manage for you.

Focus
Exposure if you are taking a scene with normal
tonal range. If your subject is predominantly
light or dark your camera will try to make it medium
gray so you will need to dial in some exposure offset.

Exposure is determined by three variables,
ISO (sensitivity to light)
Shutter speed (Faster shutter speeds stop movement better)
As dolls rarely move you don't need fast shutter speeds except
to minimize camera movement.
Aperture (F stop) a higher f stop lets in less light but gives deeper
depth of field.

As your experience increases you will want to learn how to manage
these factors to optimize your final images. As noted above your camera
can manage this while you're learning the rest of your craft.

Do not let the camera choose color balance. Look around you; see what
sort of illumination is falling on your subject and choose the most
appropriate White Balance setting.

Yes, composition is important!

Yes Lighting is important!

 

I would say look for YouTube videos on your particular camera. I myself either use the auto setting or if you don't like the flash popping up a lot try the other settings that remove the flash. Also if you don't have a owners manual you can download it from internet and read it on computer.

 

OK. I am going to be the one to say it; read the manual. There are also lots of books and videos (as has been said) to help you. I just looked, and there is a Canon 550D for Dummies. I very much like that series of books. There is a lot to learn, but it will take you through it step by step.

And, I shoot on manual, for the sake of keeping the same settings shot to shot in the same set. You don't have to. Aperture priority is just fine to start off with. And lighting and composition are fundamental.

Get stuck in!

 

Lots of Youtube videos for different themes and reading the manual is very helpful, I learnt to use my Nikon d5300 this way
I usually use portrait mode (no flash), with high ISO settings at the interiors and lower ones outside. I don't know which lenses you are uses, but for doll portraits, I recommand to use 50mm or higher (the 85mm lenses for Nikon are amazing, I don't know about Canon).
Hope this helps!

 

Ken rockwell has really good basic camera tutorials on a lot of canon camera. He walks you through the set up as well. You can google your camera and his name and it should come up. Looking through the manual might help, if you don't have it they can be found online.