If you already own a custom domain for your business, typically you can easily set up a redirect (also sometimes referred to as domain forwarding) with your domain or hosting provider so that you can use your own preferred URL on signage and within SMS messages and emails. Many providers will also allow you to add an additional sub-domain (also sometimes referred to as a "CNAME" record, ie. https://waitlist.yourdomain.com) which you could create and then have redirected/forward to your Waitwhile URL.
This process does not require any additional setup within your Waitwhile account and should be handled completely through your domain or hosting provider, though the process may vary slightly depending on what provider you are using. If you do not already have a purchased custom domain and would like to acquire one specifically to use for your Waitwhile pages, one can be purchased through many different domain providers such as Google Domains, GoDaddy, and Namecheap.
Domain redirect/forwarding is only available for public pages (such as your public check-in, welcome, and booking pages) and cannot currently be used for any pages within the backend Waitwhile app interface. You can find the URLs for your public pages under:
Settings > Waitlist > Public Waitlist (or Check-in)
Settings > Bookings > Online Scheduling
Redirect set-up guides for a few of the most popular domain providers