During the free trial, you can choose between the Basic and Essential plans based on your usage. 

Here's how you can upgrade to a paid plan during the free trial:

• Go to Settings > User > Billing > Subscription
• Choose between Basic and Essential plans for self-checkout
• Click on Upgrade
• Select the number of users 
• Click on Proceed to Checkout 
• Add your Billing Address and Payment Details
• Click on Subscribe to complete the transaction 

Your account is now upgraded and ready to use!