Construct Triangles and Quadrilaterals in Cabri Jr.
Three points determine a triangle and four points determine a quadrilateral. So the construction of each is quite similar. To construct a triangle or quadrilateral in the Cabri Jr. geometry application on the TI84 Plus calculator, follow these steps:

Select the appropriate tool from the F2 menu.
To do this, press [WINDOW]. Use
to highlight the tool you wish to use and press [ENTER] to select that tool. You see a picture of that tool in the upperleft corner of the screen. The first picture illustrates that the Quad tool is active and ready for you to construct a quadrilateral.

Use the arrow keys to move the cursor to the location on the screen where you wish to construct the first point of the triangle or quadrilateral. Press [ENTER] to anchor this point.

Use the arrow keys to move the cursor to the location on the screen where you wish to construct the second point defining the triangle or quadrilateral. Press [ENTER] to anchor this point.
If you are constructing a quadrilateral, move the cursor to the location of the third point defining the quadrilateral and press [ENTER] to anchor that point.
As you move the cursor, the sides of the triangle or quadrilateral appear as dotted lines indicating that the construction is not yet complete. This is illustrated in the first picture for the construction of a quadrilateral.

Use the arrow keys to move the cursor to the location on the screen where you wish to construct the last point defining the triangle or quadrilateral.
As you move the cursor, the triangle or quadrilateral appears on the screen as dotted lines indicating that the construction is not yet complete. The second picture illustrates this step when constructing a quadrilateral.

Press [ENTER] to complete the construction of the triangle or quadrilateral.
The figure appears as solid lines indicating that the construction is complete. This is illustrated in the third picture.
After constructing a triangle or quadrilateral, the tool you were using remains active until you deactivate it. So if you want to construct more objects of the same kind, just repeat Steps 2 through 5. When you are finished using that tool, you deactivate it by pressing [CLEAR] or by selecting another menu item.