You'll need to have Developer permissions for Google Rooms to get the Derive and Edit options. Please fill out the request form to request permission.

1 - Find a gadget renderable object in the catalog. Here's a few:
 

Jumbotron
Wall mounted screen
 

You can find more by searching the catalog for "gadget"

2 - Select "Derive new product"

 

This will load the Object Editor (OE for short)
3 - Change the name and description fields

4 - Go to the parts tab

5 - Click the Gadget URL field. 

Enter a Gadget URL from this list. 

6 - The Gadget can also be stored locally on your machine for testing. Other people won't be able to see a gadget local to your machine.
If your Gadget is in the same directory as your Lively client, you can enter the name of your Gadget. If your Gadget is somewhere else, you need to enter the full path and file name. 

 

For example "C:\Program Files\Google\Lively\ImHome.gg" would be entered as "ImHome.gg"

and "C:\Gadgets\mygadget.gg" would be entered as "C:\Gadgets\mygadget.gg"

7 - Click Reload Gadget
8 - Click Gadget Options and fill out your options

9 - Click Save
10 - Click View in Warehouse to see your new object in the warehouse