I’ve not quite figured out how to do this in wupp yet, despite using it for a couple of years!
I currently use google forms. When an enquiry comes through via website or ASLTIP, I send an email with some details like waiting times, session costs etc and also a link to add to waiting list. The link takes them to a google form where they input different details such as age, concerns, other involved etc (you can choose what questions you ask them when you design your form). This is automatically transfers into a spreadsheet so at the end of the week / fortnight I open the spreadsheet and see anyone who has requested to be added to waiting list.
Sounds a bit long winded there but it’s actually super easy!