To conjugate a verb is to modify it so that it is in the correct tense. For example, if you were talking about something that happened yesterday, you would need to make sure you conjugated your verbs into a past tense. In English, an example would be:
Now, I <em>eat</em> breakfast. (The verb TO EAT is conjugated to the <u>present tense</u> because the action is taking place <u>now)</u>
Yesterday, I <em>ate</em> breakfast. (The verb TO EAT is conjugated to the <u>past tense</u> because the action took place before)