Tap the “+Note” button in the lower left corner. The keyboard should come up and a space to create a new note should appear from the right. Now you can dictate or type a new note. Tap the “Done” to save the note, “Cancel” to go back without saving.
Tags are created by prefixing words with either a “Hash tag” (#) or a “At sign” (@). The convention is # is used for subjects and @ for names.
Note the word suggestion buttons above the keyboard and the tag suggestion buttons above that. The “+1” button adds a +1 at the start of a note. This tells #Notes to number this note based on numbering in other note with identical tags. You can scroll the tag buttons to see the last 10 tags you have used.