There are tons of youtube tutorials on Inkscape as far as the drawing tools go. It took a little practice to learn the best ways, for me to draw, edit and trace plans but it is not actually difficult. Just not intuitive if you have now CAD or Paint experience.
At the bottom of your working view there should be a small "window" that shows the current layer and has a "lock" icon next to it. Click the lock to lock the layer currently being viewed, then use the layer button at the top of the main window to add a second layer over top of the first. You will be working on the second, unlocked layer.