English has different forms of words that convey different meanings.
1. For instance, the third person singular verb in English has an -s on the end.
He sits on the bus, while I stand, and they hold on.
2. Adding -ing to a verb means that it is happening in the present time.
He is sitting on the bus right now.
3. Adding –ed to a verb means that it happened in the past.
They danced in the moonlight.
English has a number of irregular verb forms, though, so this rule isn’t always going to work! Here is a great resource for irregular verb forms: Irregular Verbs
Incorrect: He sitted on the bus.
Correct: He sat on the bus.
How can I edit for the wrong form of a word?
There is no easy way to edit for this error, except to read each word of your paper carefully. You can also ask someone else to read it specifically for this error.