Recently signed up for the free web version of this, and it’s all as clear as mud 
.
I looked at many examples and lessons, but couldn’t even change dimensions in that bottom right box.
Managed an image in canva with what I’m trying to do.
Lean to shed floor and walls.pdf (53.8 KB)
https://learn.sketchup.com/courses/sketchup-web-fundamentals-part1
You will learn that you don’t click to enter the dimensions box in the lower right… you just type, then press enter.
Once you understand the basics something like this should be easy for you to model.
The measurements box is unintuitive, but How to Make a Shed in SketchUp explains how to use it really well at 2:20 - 3:00. You can use m for units instead of ’ as you’re not making a shed in the 1850s 
To get your roof angled as desired, the protractor tool will be useful to create a construction line to move your roof edge to. That’s also not immediately obvious but plenty of YouTube videos on how to use it (web is the same as desktop for this tool), for example SketchUp Training Series: Protractor tool at 2:05 (the text entry supports both degrees and ratios, not just the ratios used in that video).
To get a precise 1:80 slope, using 0.72° is OK but to totally precise.
Use a calculator and do:
80
1/x
arctan
You get 0.716159945
There is a much faster way since SU understand slopes as A:B like 16:12, you can use 1:80 with the rotation protractor.
So, start with a horizontal line then rotate it using 1:80 as the rotation angle.
Thanks for the replies, people.
I suppose no one knows a shortcut or cheatsheet. 
Tap right arrow three times, pause for a count of two, tap left arrow once then orbit 360 and flip 180, count to six manually, jump back three steps then multiply 2 by 3 with a calculator and turn your head slightly to the left. Then you should be able to access the Campus and learn the basics.
What, no hoops to jump through?
Have you read the last line of my post?
It can be done so quickly using basic tools that I don’t see why a shortcut is required.
I guess you could also hire someone to model it for you.
Click on the scenes tabs of this SU file for ideas.
Shed with a slanted roof.skp (4.7 MB)
Thank you.
