Step 1: Login to your WooCommerce backend, and go to
WooCommerce > Settings > Advanced from the left side bar:
 
Step 2: Click “REST API”, and then click “Add Key”
 
 
Step 3: Fill out the following fields -
Description: OneCart
User: Select the admin user
Permissions: Read/Write
 

Then click “Generate API key”
 
Step 4: You must save both the API Key and API Secret.
 
1. WooCommerce website URL
2. API Key
3. API Secret
 
Step 5: Next, click “Webhooks”, and then “Add Webhook”
 
 
Step 6: You will be adding two webhooks.
Fill out the fields as follows:
1st Webhook: Order Processing
Name: OneCart Order Processing
Status: Active
Topic: Order created
Delivery URL: https://app.getonecart.com/receive_woocommerce_orders
Secret: <LEAVE BLANK>
API Version: WP REST API Integration v3
 
 
2nd Webhook: Order Update
Name: OneCart Order Update
Status: Active
Topic: Order updated
Delivery URL: https://app.getonecart.com/receive_woocommerce_orders
Secret: <LEAVE BLANK>
API Version: WP REST API Integration v3
 
Step 7: Finally, click “Legacy API” and make sure “Legacy API” is checked on:
 
Step 8: Use the information that you retrieved earlier to key them in here - https://app.getonecart.com/shops/new?platform=WooCommerce
Alternatively, you go to Settings > My Platforms > Manage Connections > Add New and click on WooCommerce'
 
 
Click 'Save' and you are all done! :)