Past simple is used to talk about completed actions or situation in the past.
The actions are begun and ended at a particular time in the past.
(ex : on Monday, last night, two months ago, yesterday .....)
When we talk about an action that occurred over a period of time but was
completed in the past, we use the past simple

(ex) I finished my homework last night.
(ex) She came to a school at 11 o'clock.

(ex) She studied very hard after the lesson last night. 
(ex) What did you do at the weekend? I went to a cinema.

When we talk about an activity that took place regularly in the past.

(ex) She got up at 8 o'clock. 
(ex) He had a lunch at 12 o'clock.

When we talk about history, of course, we use the past simple.

(ex) Columbus discovered America continent in 1492.
(ex) China invented paper.

When we use the past simple, we use the past verb form. Usually the past simple
ends in -ed, but many verbs are irregular.
Click -> the list of irregular verbs

(ex) He was very thirsty, so he bought a bottle of water. (irregular verb)
(ex) She wanted to study in Australia. (regular verb)