- coming from the homescreen and setting up a new tile / smart folder
- viewing items in a list (e.g. your email inbox)
When viewing items in a list, you can tap on the head line, for example "Email/Inbox/" and you can start the Filterer:
On the lower right you get a preview of how many results there will be, on the left ("Add filter") you can add another filter item to further reduce the results:
Tap on the right icon ">" to dig deeper in that category, tap the name on the left to select that item.
When done, tap "OK" to see your results.