Some verbs can be changed from their present form to the past tense with the addition of -ed. It is important to note that “ed” should only be added to the verb if it ends with a consonant. If it ends with a vowel, -d should be added.
Some examples include: watched (watch), worked (work), cooked (cook), danced (dance), studied (study), planned (plan), etc.
Example sentences:
Some irregular verbs, however, have past forms that do not end in -ed. As a result, adding -ed to their current form is not always possible. For instance, took is the past tense of take; sang is the past tense of sing; gave is the past tense of give; etc. However, you will need to learn the past tense of these irregular verbs yourself as you continue with your English learning. The good news is that when you know them, their past tense forms don’t change, irrespective of how they are used.
Here are some more examples:
Past simple vs. past continuous