Yes, this is imperative, a 'command structure'.
"Weźcie" (it's Ź and not Ż, an 'accent' and not a dot) is 2nd person plural. "Weź" would be 2nd person singular.
Imperative for 3rd person is constructed differently and I don't think it's taught in this course, although frankly, it's a lot simpler. You use the word "Niech" and then use a form for 3rd person.
So you'd have "On weźmie" (He will take) and "Oni wezmą" (They will take), and then "Niech on weźmie" (Let him take - this would be the imperative?) and "Niech oni wezmą" (Let them take).
(It's "WILL take" because it's perfective, and perfective verbs do not have present tense.)