Going to is used when someone has the intention to do something in the future, is making a prediction of the future or when something is about to happen. 

The structure of going to is: subject + be (conjugated) + going + to + infinitive. The verb be is conjugated like this:

I am, You are, He/She is, We are, They are

For the negative form, the not comes after the conjugated form of be and before going to.