SketchUp Go - unable to specify dimensions

I am new to SketchUp and watching tutorials to get my project up and running. Everything I have seen shows how easy it is to add the dimensions to a specific shape. I have a paid version of SketchUp Go.

The dimension box on the bottom right hand side, displays the current measurements of my object but if I enter the specific measurements I need - nothing happens.

Please help - this will change my life

Don’t click in the box.
Sketchup is always listening for input, so when a tool is active you simply type what you want and hit enter/return.
So to create a rectangle get the rectangle tool click and release to start a shape, move the cursor roughly in the direction you want to go then simply let go of the mouse and type in mid air 50,70 and hit enter. This will make a rectangle 50 x 70 of whatever units your model is set to. You can add the unit when typing as well if you wish, and that can be a mix of imperial and metric. Just don’t click in the box. Also check what the divider is that shows in the box and use that, I have shown a , here as that is what my regional settings are, but in other regions the divider is ;
You can keep changing the size but typing again until such time as you activate another tool.

OMG thank you - watched so many videos and didn’t pick that move