Confused about the Polish Imperative

I am confused about the imperative. For example would I say "Przestaj narzekac" or "Przestaj narzekaj"? I need more info on the imperative. Dzienki!

przestań narzekać ;)

Is przestań the imperative? Also does both verbs have to be imperative because I am confused because some instances only the first verb is imperative or sometimes both verbs are imperative (daj spokoj?).

Spokoj is peace and is a noun not a verb. Niech pan przeczyta gramatykę is also, I think a form of the imperative expressed in a different way. Przesań, to stop doing something is a very good example of the imperative but przeczytaj dalej is also an example of the impreritive. Nie patrz sie na mnie-don't look at me would be another example. Buy a good grammar course and it will explain everything in an order and that would be your best bet. Borrowing from a library can be a problem as you might like the book but you have always got to return it after a few weeks.

no, in the combination of two verbs (like in your example "przestań narzekać") the first is imperative, the second infinitive.

but the imperative gets different forms for different persons:

Sing.
1. -
2. Przestań narzekać (Stop complaining)
3. Niech (on/ona) przestanie narzekać (Let him/her stop complaining)

Plural
1. Przestańmy narzekać (Let's stop complaining)
2. Przestańcie narzekać (Stop complaining)
3. Niech (oni/one) przestaną narzekać (Let them stop complaining)

3rd person isn't technically imperative, but I forgot what it is, but it has the same function.