Once you've created a valid invoice, you can generate a URL to send directly to your client by following these steps:
If you have already sent your invoice to your client via email, but would like to send it via URL, then you can select the "View Client Invoice" option from the dropdown, and send them that link:
Pro tip: before sending your invoice, always watch out for the currency you're sending the invoice in. Your invoices will be charged a foreign exchange fee if the currency doesn't match your payment country's currency. You can learn more about the FX fees here.