Squids is not intended to be extremely flexible or powerful. It's designed to be extremely easy to learn and use. As such, you won't be able to make any game you can imagine with it. But you can make some really great games and you will learn a lot about how game engines and game development work.
Squids games are written in Javascript and run within a web page. Squids doesn't provide any editors or other tools. You must know how to create a web page and include javascript files.
You are strongly urged to start by downloading the example game, reading through the code, and starting with that as template. It consists of: