The W9 form can be found within the onboarding form underneath the Clients tab.
In order to edit the form, select the 'Pen' icon on the top right-hand side of the screen. After you input your 'Legal Name', a form will become available to sign via e-signature.
Note that sometimes the form might not show after signing - this is due to it waiting on a follow-up signature from your hiring manager. Once this is completed, the document will appear and you'll be able to download a copy from the same page you signed it originally.