Older Windows 10 versions will have it at the top of the Start menu along with the account name.

You can also go to “Settings > Accounts > Your info”. Now, skip to Method 2 if you want to use an existing picture. Skip to Method 3 if you want to take a new photo for use.

Using a video as your avatar is pointless as it will extract and use the last frame from the video. Thus, taking a photo is simpler and more efficient.

Keep in mind that Windows automatically rounds the corners of user avatars. The outcome is that the very edges to be cut off. Customarily, previous Windows versions had a square user account pictures.