Past simple - 1

With regular verbs you make the simple past by adding '-ed'.
Unfortunately, there are a number of irregular verbs and with those, this rule doesn't apply.
The irregular verbs have their own form that you have to memorize/study.

present tense

past tense

to be

was/were

to buy

bought

to come

came

to do

did

to drink

drank

to eat

ate

to feel

felt

to find

found

to get

got

to give

gave

to go

went

to know

knew

to leave

left

to make

made

to meet

met

to read

read

to say

said

to see

saw

to sit

sat

to sleep

slept

to take

took

to teach

taught

to tell

told

to think

thought

to understand

understood

to wear

wore

to write

wrote


You can find various lists of irregular verbs on the internet.