Once you have marked notes with note tags, you can then easily find them by using the Tags Summary task pane.
On the View menu, click (or tap) All Tagged Notes. The Tags Summary task pane displays a list of notes that you have tagged, as well as the following options:
Group or sort note tags by tag name, section, title, note text, or date (OneNote automatically dates each page for you as it's created).
Collapse or expand each group of tags by using the plus or minus sign next to the tag group.
Which parts of a notebook or notebooks to include in the summary.
Note tags in the task pane are linked to the note tags on pages. You can jump straight to a specific note by clicking the note tag link in the task pane.
Tip If you're using tags with check boxes, you can save time by selecting or clearing the check boxes in the task pane rather than going to the relevant page.