For regular verbs, you need to add "-ed" or "-d" in its base form. And for irregular verbs, is one that does not form its simple past tense or its past participle by adding "-ed" or "-d" to the base form. There are specific form of it, like, the verb "cut". To have it in past tense, you don't need to add "-ed" or "-d", leaving it as it is will give you its past tense. This is somewhat tricky, so you need to be careful in changing this type of verb into its past tense.
