I've done for this a couple years and it has helped a couple of my classes with their grammar and communication.
First, introduce the activity using the PowerPoint. Practice the "Do you have a...?" and "Are you from...?" questions with the students at least two times. Students can answer with "Yes, I do." or "No, I don't." (for "have" questions) and "Yes, I am" and "No, I'm not" (for "from" questions.)
Then demonstrate with the HRT. When the students find someone from a certain country, they can put a circle or write their classmate's name in the box. The goal is to ask as many as possible. Give the students 5 minutes to start walking around and talking. If they need a little more time, give them 2 more minutes. After they are seated again, you and the teacher can ask volunteers or random students "Do you have...?" and "Are you from...?" questions.
For the new words (specifically the textbooks and gym clothes), I let the students use Japanese. So long as they practice the questions using primarily English (Do you have a/an...), then everything is golden.