This means that you can use these projects in a very interactive and exploratory manner, no need to have the docs open in a separate window and making sure you don't make a typo.
Installation is fairly simple as it just works on top of npm. So as an example you can install type definitions for jquery simply as:
npm install @types/jquery --save-dev
@types supports both global and module type definitions.
By default any definitions that support global consumption are included automatically. E.g. for jquery you should be able to just start using $globally in your project.
However, for libraries (like jquery) I generally recommend using modules:
After installation, no special configuration is required really. You just use it like a module e.g.:
import*as $ from"jquery";
// Use $ at will in this module :)
As can be seen, having a definition that allows global leak-in automatically can be a problem for some teams. So you can choose to explicitly only bring in the types that make sense using the tsconfig.jsoncompilerOptions.types e.g.:
The above shows a sample where only jquery will be allowed to be used. Even if the person installs another definition like npm install @types/node its globals (e.g. process) will not leak into your code until you add them to the tsconfig.json types option.