To create a new Jam on your computer, go to jamboard.google.com and click the orange + icon on the bottom right corner.
You can also start a new Jam from your Google Drive:
+ New > More > Google Jamboard
Sharing Your Jam
To share your Jamboard with others, click Share in the top right corner of your Jam.
Option 1: Enter the email addresses of the specific users you’d like to invite to participate in the jam. Be sure to give these users “Editor” privileges.
Option 2: Change the privacy settings and copy the link to share with your users. Be sure to change the access from Viewer to Editor.
