When using a mouse with a desktop, or laptop, computer you have access to physical buttons to perform left and right mouse clicks to carry out certain tasks.
However if you are using a laptop [without a physical mouse] then things are a little different.
Laptops have touchpads / trackpads that let you direct the cursor to a desired position. Some are accompanied by physical left / right buttons immediately below them, while others simulate left/right key depressions with the pad itself by pressing down in the bottom left or right corners.
In the latter case, when using Cloudready, you may find that the desired left / right key depressions are not working [this is down to your physical hardware] but in most cases you should find that holding down the Alt key before doing the left / right key depression will enable it to action correctly.
Click here for an article from ChromeUnboxed named "Work Smarter, Not Harder, with your Chromebook Keyboard and Trackpad" - it's quite short and worth reading for a couple of tips you may not have heard about.
Click here for a Google Support page named "Use your Chromebook touchpad" for more details.