You'll need to create an API key. You'll do it on Fleetio's API keys page. If you can't open that page or create a key there, ask your Fleetio administrator to do this step for you.
Open Fleetio's API keys page at https://secure.fleetio.com/api_keys.
3.
Generate a new API key.
4.
Copy the key and paste it somewhere safe for a moment. A password manager is best.
The same page also shows your Account-Token. You usually don't need it. See Step 2.
Treat the key like a password. Anyone who has it can act on your Fleetio account. Don't email it, don't put it in a chat message, don't save it in a shared document.
Account token (only if the key reaches several accounts): optional, under Advanced settings. Leave it empty in most cases: Makini finds your account from the key on its own. Fill it in only if your key gives access to more than one Fleetio account, using the Account-Token of the account you want to connect, from the same API keys page.