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If you have not already created a note or want to create a new note to add tags to, select the "New Note" tab and follow the onscreen instructions to do so. Click "Save" in the top-right corner to add the tags. " input field to select and add tags that you have already created for other notes.
Launch the Evernote iPhone or iPod touch app from your device's home screen. Tap the "Notes" tab at the bottom of your screen. Select a note you want to add tags to. Select the pencil icon from the bottom right hand corner. Tap the "Tags" input field and type new tags separated using commas. Alternatively, you can tap the blue arrow next to the "Tags: