The verb "do" is a helping verb. We add it to the simple form of a verb to make questions and negatives in the present tense and the past tense.

Examples:

I don't work on the weekend. (present tense negative).

I didn't work last weekend. (past tense negative)

He doesn't like to go to the store. (present tense negative)

He didn't like to go to the store when he was younger. (past tense negative).

They don't have any money. (present tense negative)

They didn't have any money last week. (past tense negative.)

Note: "Do" is also used as a main verb for activities, such as housework, cleaning, studying, research, business, and shopping.

Examples:

I don't do the dishes every night. I didn't do the dishes last night.

She doesn't do her grocery shopping at Cub. She didn't do her grocery shopping yesterday.

They do not do their homework at the library. They didn't do their homework last night.

Their company doesn't do business in Minnesota. They never did business here.

The past tense form of "do" is "did." Did + not = didn't

Examples:

I didn't go to work yesterday.

She didn't take the bus to work.

Separating the contraction creates emphasis

Examples:

I did not want to do the dishes last night. I do not want to do them now!

He does not have his license! He never did get it!

Please, do not put that hot pan on the counter!

Never put did + ____ing

He did going  to work last night. (incorrect)

He went to work last night. ( correct )

Avoid bad American grammar!

She don't go to work on Sunday. (She doesn't go to work on Sunday.)

It don't matter to me. (It doesn't matter to me.)

He don't know. (He doesn't know.)