When using the PDA portal, there is no way to reset a tool (i.e. go back to its start page). The name of the tool does appear in the navigation toolbar shown at the top of every page, but is not clickable and has a "?" next to it
For example, the toolbar may look something like this:
Sites > Test Site > Forums | Log Out
The "Forums" part is not clickable, making the only way to go back to the start page of a tool a roundablut approach - going back to the site's main page and clicking the tool there.