You can upload videos of any size into the pop-up and resize the pop-up's width as needed. To upload a video, you'll need a video stream ID. For more information on obtaining a stream ID, refer to this article. Here's how to add a video to your pop-up:

1. In the tools builder interface, click on Pop up.

2. Set the pop up type to Video.

3. Scroll down till you find video text area and paste the stream ID into the text area.

4. Adjust the pop up's width according to your preference.

You can also customize the pop-up further using the other options available in the pop-up interface. Make sure to save and preview the Videoform. If you are satisfied with your design, you can install the tool on your Website.