How to use a gas stove without getting carbon monoxide poisoning?

For god's sake, people cook with gas all the time. Just turn it on and cook, no other safeguards are needed.

CO results from incomplete combustion. Complete combustion burns any CO into CO2. Unless your house is really air tight you won't get much CO.

You can get an inexpensive CO detector. 

When there is a blue flame complete combustion takes place and no CO is produced . Your safe . If you want to purchase a CO monitor that will tell you if CO is present

If you need to learn on how to turn one one there is YouTube .

For your normal cooking, an hour or two. Even without a direct exhaust. It will be fine in the vast majority of cases. If you are cooking say a turkey, and it will be on for an extended period of time. It is best to have a window cracked or something. Many places now require a direct vent hood vent. Which if you have, just turn it on while using the oven. At one point many gas stoves were touted as supplemental heating sources. Or heating substitutes in case the power went out and such. Millions used them as such, leaving them on all day and night. That is when some issue started to pop up. So unless you are doing something along those lines, you'll be fine.

It's completely safe. Just turn it on. If you're really paranoid, you can run a fan or crack a window when using it. But I've been using gas stoves for 30+ years without incident. I even picked my current house because it had a gas stove while the number two candidate, while better in some ways, had electric.

i would ask your parents about it, or get a microwave and use that

Unless it isn't operating properly, it won't produce enough CO to be an issue.

There SHOULD be an exhaust fan above the stove that is more than sufficient to remove what little CO is produced.

If it makes you feel safer, you can get a CO detector.

It's perfectly safe. Just turn on the oven or the burners and cook.