Sign up for an account on https://www.taxjar.com?rfsn=801596.286cf3
You should see a box pop up about integrations. Select "do it yourself with SmartCalcs API" (If you don't see this box pop up, you should be able to complete the next step by going to Account > SmartCalcs API)
3. Generat an API Token
4. Copy your Token
5. Then, on your AmmoReady account, go to Settings > Add ons. Select TaxJar, and Paste your API Token in the text box.
6. Then click Install Addon.