...
You should have something like this:
Dimensions
Now we will specify the appropriate dimensions and constraints. Below is the summary of geometry of the pipe:
Length: 1 m
Height: 0.5m
Under Sketching Toolboxes, select Dimensionstab, use the default dimensioning tools. Then click on the lines and drag upwards or sideways as the case may be to place the dimensions
Go to Step 3: Mesh