Airtable is a spreadsheet-database hybrid. Note that because val.town uses Deno, an unofficial client library has to be used.
On the homepage, click Start from scratch to create a base:

If prompted with automatic setup, click Skip. You should get a new base with a blank table.

Adjust the table fields as you want (note that this isn’t covered by this guide).
Click on your profile icon, then on Developer hub:

Click Create new token.

Fill out the fields:
valtown.data.records:read and data.records:write.Lastly, click Create token. Here’s an example of how your settings could probably look like:

Copy your token and click Done.

Go to val.town, click on your username and then on Secrets: