Use "Place Vertices" to place unconnected vertices. When you add 3 they will automatically become a triangle. Use "Select Vertices" to select and move vertices (move by clicking and dragging in an empty area of the canvas). Use "Make Triangles" to create triangles from existing vertices (including unconnected). Use "Select Triangles" to select set the texture and texture UV coords of a triangle. Use "See Results" to render the rasterized image.
