Once you’ve downloaded the app, the Signature macro will appear immediately in your list of Confluence macros.
In edit mode, use the / key or the + button at the top to find it.
Add the macro to your page and it’ll appear, by default, as a signature box. You can change it to be a box to enter a date, initials, text, or a checkbox instead if you wish. Add more signature fields if there are more participants who need to sign. Add other fields if the signee needs to add more details, e.g. a date.
Publish the page and you’re ready to send your document for signing.