Hi, nice that you want to paint in oils.First you have to get the materials, then choose an easy picture to paint, and there you go!you can start painting.
Materials:
canvas boards to start with,
A set of oil paint tubes if you are going to be serious about it, or a few colors like red,blue,yellow,white and black.
Oil painting brushes , round ,flat, thin and one two inch brush.
A small bottle of linseed oil
Turpentine to clean the brushes.Nowadays it is considered to be polluting the air with strong odour so sunflower oil an organic oil is suggested by some.
A rag cloth to wipe the brushes after rinsing them with turp.
Varnish to give that protective cover, which has to be given only after three months to allow time to dry completely before framing.
All of these you can get in Micheals or any art store.
You can use the linseed oil to thin the paint.It takes long time to dry, so each layer should be painted only after the previous one dries, unless you want to blend two colors.
Finally after buying the materials, try to watch oil painting videos in the "you tube", it will be really enlightening and inspiring.
I am not an expert in oils though I have attempted a couple of pictures. I think that these basic facts will help you to take that leap forward.
Best wishes, and hoping to see your works soon.