When sending a bug report, your user will have an initial screenshot attached by default (they can choose to remove or replace it). They can then attach screenshots up to a total of 4.
The bug report page has a built-in screenshot tool that lets your users navigate to a specific page then take the screenshot using the SDK. The user will then be able to annotate any of their screenshots.
If you are on the free plan, your user is limited to 1 screenshot attachment, but on higher plans, adding multiple attachments becomes possible.