The verb can is used to express ability to do something and to ask for permission.
I can sing quite well
Can we go out on Saturday?
The verb can is special. It doesn't add the '-s' in the third person singular
She can dance very well
It is always followed by another verb in the plain infinitive, that is, in the infinitive without 'to' .
They can play tennis
*NOT they can
To make the negative we add not to the verb and to make questions we just swap places between subject and verb.
We can't go out tonight
Can you play the guitar?
Note that in the negative it is either can't or cannot but NOT
Watch the video and sing with the busy beavers. Remember that songs are good practice to learn. Pay attention to the pronunciation!!