stream overlay is a transparent (PNG) image that is 'overlaid' on top of game / Livestream content. Most commonly, these graphics are positioned around the edges of the screen, so that the center of the screen remains unobstructed to showcase the gameplay. 

1. Open Vmix on your computer.

2. Add you inputs such as video, camera, photos, and etc. Once you added your inputs then you can now click overlay at the bottom right side of the VMIX. 

3. In the overlay box you wil be seeing the following. 

1. Top part

> The number is where you can set on what number you will be setting to trigger the overlay. 

> Either you can set the overlay to be full screen or picture in picture. Most of the time we use PictureInPicture

> You can set the effect of transition and you can set the duration of the overlay

2.Middle part

> The left side you can set the size and location of the over lay and you can see it on the right box.

> You can also manually resize and relocate the overlay using you mouse to drag the icon. To resize the overlay you can press SHIFT then press and hold the mouse cursor and drag it to resize. 

3. Once the overlay is set you can press OKAY.

4. Once the ovelay is set you can use the numbers at the bottom of the inputs to trigger the overlay. Choose the number depending on where you set the overlay and on the right side you will see the overlay once triggered.