The Canvas is infinite in size; you can scroll as far as you want vertically or horizontally, so you have complete freedom on how you set up your drawing area.
If you’d like to define a fixed frame for your Canvas, go to Settings and adjust the Page Size.
Navigating around the Canvas is easy. You can use the scroll-wheel on your mouse or a trackpad to scroll in either direction. You can also hold down the spacebar and click and drag to pan around as well.
It’s likely that you will want to zoom in to your document in order to see it in more detail. Or perhaps zoom out, to see the entire Canvas. This is something that is quite important, so there are many ways to zoom in WireframeApp.
You can simply zoom by pressing on the plus and minus buttons next to the Zoom item in the toolbar. The zoom level will increase as you zoom in, and decrease as you zoom out. The maximum zoom level is 200%, and minimum is 25%.
Here are some more handy shortcuts for the Zoom tool: