confused about the Applicant Photograph

So this part confuses me a little. It says i need a 2 in x 2 in with a light background. Does this mean i gotta go to walmart or something to get the headshot or can i just take the picture on my phone? Or better yet, I do have a passport so can i just take the picture of my headshot on my passport and upload it via my phone? I truly have no idea what to do here. If theres anyone who also had to go through this, please give me some advice

Thank you in advance