Rotating the model a little counter-clockwise makes it MUCH easier to work with as the graphic goes away.
With that let’s add some initial dimensions. These mean NOTHING .. they are just a place to start. Depending on your resolution of your graphic they can be anything. Click the Dimension Tool (there isn’t a hotkey for this tool). It is to the right of the Tape Measure Tool – the number 3 between two dimension lines. With the tool selected hover over the ends of the lines for the ladder. Click on a line end (green dot) then move to another to set the dimension then drag to where you want it. You can move this later any time by selecting the dimension and using Move (M).
How wide is a ladder? Got me – anything from 16 in. to 22 in. BUT .. rungs are spaced 10 in to 12 in. Those are the ones we can use to dimension this. See the two (means nothing) dimensions .. 0.396″ and ).430″? Those.
(Note: I have my default set to Decimal Inches. You can set that default to whatever you wish by – Window –> Model Info from the menu. You can select various Formats: Architectural, Decimal, Engineering and Fractional. Selecting Decimal you can then select Inches, Feet, Millimeters, Centimeters or Meters. Me .. I usually use Decimal Inches. That’s just me. I’ll leave it at that .. for a moment longer)