There is a lattice of about a mm spacing which is implicit in the drawings and allow lines to meet quite conveniently. Once a line or arrow is drawn, you can click on it where the crosshairs show, and then click on the dashed or arrowhead styles pictures to modify it. You can also right mouse click to get a menu for that or for the line color. The simplest ways to generate lines or elements of the same size is to right click on one and use copy and then right click again for paste to get a copy that you can drag to the new location. Lines can be lengthened or shortened by clicking on the line and dragging the end boxes.
Text is entered with the text box, shown as a picture with an A in the upper left corner.
After you enter the text, a right click when the cross hairs show will allow you to go to Format Textbox to set the Fill Color to No Fill so that it does not cover the drawing beneath it. You can also set the Line Color to No Line so that there is not a box around the letter. Then when you again right click on the cross hairs in the text box, you can click on Set Autoshape Defaults to keep the same defaults on all future text boxes. Superscripts can be entered by simultaneously typing ctrl-equal. These are the opposite for direct super or sub scripts in text.