1) Firstly, create a new post or page, and insert into content of the page this shortcode:
You can just click at the booking button at edit toolbar and then at popup dialog select second tab for inserting this shortcode or just write manually it. Publish or update page and COPY the URL to this page.
Important! Please note, if you open this page directly, you will see this warning "You do not set any parameters for booking editing". It's because system allow to open this page only from link(s) in email templates, which your website visitor had to received, after he/she made the booking (inside of that link will be specific parameter (secret HASH) for the identification of the booking).
2) Now, open the general booking settings page and at the "Advanced section" for field: "URL to edit bookings" write (paste) the URL to the page from point #1. Save the changes of this settings page.
3) Open Booking > Settings > Emails page and inside of email template(s), where it's possible (you can check it at help section under the each email template), you can use these shortcodes (for the inserting links into the email templates), which are sending to the visitors:
[visitorbookingediturl] - inserting link of booking editing by visitor at client side of site,
[visitorbookingcancelurl] - inserting link for booking cancellation by visitor at client side of site,
[visitorbookingpayurl] - inserting link to payment page for visitor at client side of site.
4) You can test it for a new bookings.