You can print Sendle labels via ReadyToShip by creating a free Sendle account and connecting it as a carrier in ReadyToShip.
Step 1: Create a Sendle account
If you don't have a Sendle account, you can create one here.
Step 2: Go to your Account Settings in Sendle
Step 3: Generate an API Key
Important: To enable the API tab in your Sendle Account settings, you need to Complete the Dangerous Goods declaration. You can find this on the 'Sending details' tab under Account Settings.
Add a credit card to your account on the Billing page.
Go to the API tab on the My Account page and generate a new API key
Enter your store's domain name and click Claim Access to generate your API key.
The API Key and the Sendle ID will need to be entered into the setup process in ReadyToShip in the next step.
Step 4: Add Sendle as a Carrier in ReadyToShip
In ReadyToShip, go to Settings ⇒ Carriers ⇒ Add Carrier, and click Sendle
You will be shown the Sendle connection page (Step 1) in the process.
This is where you need to enter your API Key and Sendle ID from Step 3.
And that's it! Once you have entered payment details in your Sendle account, ReadyToShip will be able to show quotes on your shipments and print labels for Sendle.