Firstselect the viewport and in the SketchUp Model panel on the right, select a suitable scale for the project and the paper size. Then drag the edges of the viewport to show the model. Here I selected 1:20 which is clearly too large for the paper size you have selected but you can see the idea.
If you don’t care about the scale of the drawing you can just tick the box for Preserve Scale on Resize before dragging the edges of the viewport. Generally, though, it’s best to choose an appropriate scale.
No. In LayOut. Look at the SketchUp Model panel in the tray on the right side of the screen. In my gif you can see where I set the scale for the viewport.