Your monday.com boards are made up of groups of pulses. A pulse is an individual row in a group. The content of a pulse is totally up to you and will depend on what the boards plan is -- from a list of projects to weekly tasks.
To add a pulse to a board, simply click into the box which says + Create a New Item (Pulse) and type what you want the pulse to say, then press enter.
Or you can add a pulse below an existing pulse by clicking on the drop down arrow to the left of the pulse and select "Create new Pulse below".
To add a group of pulses to your board, click the arrow to the left of an existing group of pulses revealing a drop down menu. Then, click on Add a New Group, type the title of the group of pulses and click enter.