1Copy the Sheet
Use the chrome browser. No idea if others work for this.
Open the sheet and under the File menu select "Make a copy..."
name it whatever you want
2Add the code trigger
Select Tools -> Script Editor
this will open another tab. Go into that tab
look at the code to verify I am not installing anything nasty
Select Edit -> Current Project's triggers
this will open another tab in the G Suite Developer Hub
select "Add trigger" in the bottom right
Choose the function "onOpen" to run in the "Head" deployment in the "from spreadsheet" source and event type "on open"
it will prompt you to choose an account and allow permissions. choose the current account and approve the access.
3Set up your username and api key
go back to your sheet and select the Settings tab.
enter your Tindie username and api key in the indicated spots. You get the api key from the "Seller Tools" tab in your Tindie store
4See if it works
go back to the Data tab and refresh the page
If you don't have any unshipped orders - or it didn't work - it will say "no unshipped orders" in A1
If you do have some they should be listed there in all their glory
Select File -> Download as.. -> Tab-separated values
import this into your shipping software
Note that the address field supports a max of three street address lines at this time. Easy to add more, Endicia supports 7