To share videos you also need to upload them to some hosting service first. You can use drive.google.com/ or 4shared.com/ for example. In both you need an account to upload and share your files.

I will use 4shared in this example:

1.Log in to 4shared.com/

2.Click the big blue Upload field

3.Select file, press open

Once the file has uploaded, you will see a page with thumbnails of your files. If not, click the name of your account on the top right, and select "My account"

4.Hover your mouse over the thumbnail of your desired file, you should see a "Share" button appear underneath -> click it.

5.Copy the download link, and post it here in the message portion.