If you need to use a third-party library that does not have any definition file, you can start by a single-line declaration. You need to create a file with the name of the module with the extension .d.ts and add this single line:

declare module "*";

This won't give you any Intellisence, auto-completion, but the file will be importable inside your TypeScript file without any issue with the compiler. You can start with this one-line approach and then slowly move to a more elaborate definition.