Basically the modeling agency wants to see what you look like on camera (in this case on video) to see if you are photogenic and have a look they feel they can promote to clients.

A modeling agency will normally provide you with instructions for how they want you to film this video but in case you didn't get any additional instructions, here how it's generally done: 

Stand in front of a white wall. if you don't have access to a white wall, any wall that is a solid color will work. 

There should be even lighting meaning that there are no shadows that are cast over your face or body. So natural lighting is best.

You're going to record your self starting with a  close up shot of your face and  then moving back to show your full body. You should get a closeup of your face and your profile both left and right. 

For full body you should get front, back and both profiles. For the closeup shots you should say your name, age, height, measurements and maybe a little something unique about you like if you are a ballerina, play an instrument, have a unique skill, hobby, excel at a particular subject, etc. If you're tall enough for runway, you may want to do a runway walk.

You can do this video vertically or horizontally.

In most scenarios, you should wear something simple but well fitted like skinny jeans, leggings, a tank top or fitted t-shirt. Everything should be solid colors i.e. black, blue denim, white, etc. so that the focus is on you and not what you're wearing.

The whole video shouldn't be more than 2 minutes at max unless they've provided additional instructions. 

I'm a 20 year modeling industry veteran who has worked with major agencies and now manages all my client work in-house. I have worked with brands such as LA Fitness, Saatchi Art, Uoma Beauty, Sephora, Netflix and many more. I write a newsletter and offer courses helping aspiring models break into the modeling industry at the StarterModelGuide.com. Follow me on Instagram, Instagram.com/startermodelguide and Instagram.com/daisijo