Tap anything to select it. Its settings open on the right.
Change a length: tap a wall or a dimension, type the new length (19, 19.5, 19'6, 19-6 all work), press Enter. Everything past that point slides over so the building stays connected.
Drag a wall to move it. Walls attached to it stretch to follow.
Drag the blue dot on the end of a selected wall to extend or shorten it.
Doors: pick Man door or Overhead door on the left, then tap a wall. Drag a door along its wall to move it. Tap it to change the width or flip the swing.
Heaters, lights, fans, text, stairs, bathrooms: pick the tool, then tap where it goes. The tool stays on so you can drop several. Press Esc or pick Select when done.
Room labels measure the room around them on their own.
Move around: two-finger scroll to pan, pinch or the + − buttons to zoom. Drag empty space to pan.
Keys: Delete removes, Cmd+Z undoes, Cmd+D duplicates, arrow keys nudge, Esc goes back to Select.
Saving: changes save on their own into the version you are working in. Save as new version starts V2, V3… when you want a fresh one, and Make a copy copies the whole building. If you edit someone else's version, your changes become your own new version, so theirs stays as it was. Open Files to see every building, its versions, and folders.
Download PDF gives you the 11 x 17 sheet as a file.