Just got my first air-rifle so I got some newbie questions

So basically I just bought my first ever co2 rifle. And I have some questions regarding care and how to function it. Since j still haven't bought ammo nor co2 canisters for it I have some questions.

My rifle can fit according to the manual 3 co2 12g canisters. But I can only get one at the moment. So my question is, will I need all 3 to be put inside? Or will it work with only just one inserted inside? Will I have to press it inside with some device?

Also how do I maintain the external metal of the rifle to prevent rust. (when I was a little kid I had a b2 air rifle and those were quite crap and they rusted a **** ton. So I hope i can prevent that on my new rifle)
 
Normally you can get by with an empty used co2 cylinder and a new one placed in the proper location and get less shots inline type tube piercing opposite ends. Perhaps the one in magazine follow instructions which one via critical placement might be enough while leaving other co2 positions empty. 

No idea what gun you talking about though.

Black diamond CLP or Zerust or Strong Arm Sprays would do and pretty much anything's better than nothing for rust prevention.




 
Start at 1:50 he only uses one co2.

https://youtu.be/GAiJpaunCoI

Apparently only one co2 gets pierced so I suspect the other 2 are only stored in the tube to act as shims in place of that black spacer so you have 2 extra new co2s to swap positions in the field when each are used up.

https://youtu.be/H4vZvd5ZepA

https://youtu.be/H4vZvd5ZepA

Apparently this one uses 2 co2 but only one gets pierced.

https://youtu.be/7M4ls8qK_ZI