The simple past is used to express an action that started in the past and ended in the past.
Positive Form: I ate
Negative Form: I didn't eat
Question Form: Did I eat?
For regular verbs just add "ed". For irregular verbs you can use this table:
Irregular verbs list (use only the first 3 columns)
When adding "ed", you should notice these exceptions:
If the final letter is an "e", just add "d" Ex: decide --> decided
If the final letter is "y" after a consonant, the "y" becomes "i" Ex: identify --> identified
Finally, remember: If you want to speak English fluently, you should focus on listening. Even English grammar you can learn it by listening (it's the best solution)