Installing for the first time?
Before you begin, check with your domain administrator to make sure that the add-on has been whitelisted and the account you're using has sufficient API access rights.
In Google Sheets, start by going to Add-ons > Get Add-ons. Search for Gopher for Groups and select Individual Install.
Or, cut to the chase and install it directly from here.
Once installed, you can open Chrome Gopher from any Google Spreadsheet from Add-ons > Gopher for Groups > Launch Sidebar
It is important that you do NOT install the Add-On domain-wide as it will appear for ALL users.