User has a custom Lambda function that needs to be installed in their AWS Account.
Navigate the Lambda console
Click the "Create Function" button
Select the "Author from Scratch" option. By default this is "selected" although it might be a bit hard to see that initially because the "selected" option doesn't loo that much different than the other options
Give you Function a friendly name, we typically recommend prefixing the name with "fndy_" so you know that it's part of the Foundry framework.
You'll need to select the appropriate Runtime, this should be provided to you by the author of the function
Select "Choose an Existing Role" from the Role drop down
You'll need to scroll down a bit to the "Function Code" section.
Change the "Code entry type" to "Upload a .ZIP file
The Author of the Function might also provide you a "Handler Name," if none was provide you, leave it as default.
Additionally, the author of the function might provide you with "Environmental Variables," that you'll need to define.. these are Name/Value pairs that are added at the bottom.
Click Save at the top of the page, and be sure to Note the ARN at the top of page, as you'll need this create your Foundry Actions
Finally, the author might have specific timeout setting that may need to be set. Scroll further down the page to the "Basic Settings" section and adjust the Timeout information. The maximum time is 5 min 0 seconds.