When you form the negative, you use the verb "to do."
You use the form of the verb "do" that is correct for the person, number, and tense. She does, we did, I do, etc. Then you use the main form of the main verb - the infinitive, without the "to."
To swim: She swims, she does not swim.
To go: We went, we did not go
To see: I see, I do not see.
[EDITED by khoff to correct a confusing typo.)