If you haven't done so already, you must have your company's banking information setup in the Payments section of your account in order to start accepting client payments. Click here for instructions.
Step 1: Click your initials in the top right corner then choose "Account" from the listed options,
Step 2: Select the "Widgets" tab from here,
Step 3: Once you've been redirected, scroll down a bit and you will see the "Payment Form" header which includes both the URL link that you can send directly to your clients in an email, as well as the code to embed the form directly on your company website.
*Note: Clicking on "Preview in New Window" will reveal the form in a new tab of your browser; this way you can see what your clients will see before sending it to them.