When you handwrite or draw notes, OneNote typically does a good job of guessing which of your ink strokes belong together to form a selection. In some cases, this “best guess” might not be to your liking, so you can easily create a custom selection with the Lasso tool.
Navigate to a page containing multiple ink strokes.
Click Draw > Lasso Select.
Click outside of the ink strokes you want to select, and drag a circle around only the ink strokes you want to include in your selection. For example, you might select only a single handwritten word or a single character in a line of handwritten text.
After ink strokes are selected, you can apply formatting to the selection or cut or copy and then paste the selection to another location. If your ink selection contains words, you can also have OneNote convert them to typed text.