The window has three panes: the sidebar on the left, the list of notes in the middle and the open note on the right.
File ▸ New (Ctrl+N) or the + button above the list creates a note at the top of the list. The first line of a note is its title. Paragraph saves every note by itself; File ▸ Save… (Ctrl+S) saves it at once.
Click a note to open it. Shift+click and Ctrl+click select several notes. A double-click opens the note in a window of its own. Right-click a note for Star, Trash and the colors. Click the title above the list to choose the order: Date Modified, Date Created, Title (A–Z), and Starred Notes First.
The sidebar shows Notes, Recents, the Trash, the colors, the tags and the starred notes. View ▸ Sidebar (Ctrl+Shift+M) shows or hides it; View ▸ Extended Sidebar (Ctrl+Alt+Shift+M) shows the names next to the icons. Drag notes onto a color or a tag to give them that color or tag.
The Colors menu gives the selected notes one of eleven colors. Writing #word in a note adds the tag word; right-click a tag in the sidebar to rename or remove it.
The magnifying glass above the list (Ctrl+F with the list in front) searches the titles and the text of all your notes.
Trash moves a note to the Trash; in the Trash, Recover brings it back.
Help ▸ Create Sample Notes… adds a few example notes that show what Paragraph can do. Your own notes are not touched.