Install Slick-Modal for TYPO3
You simply have to install the Slick-Modal Extension for TYPO3 in Extension-Manager. Afterwards include the static Template Slick-Modal (slick_modal) within your Root-Template.
As mentioned in the Slick-Modal Extension description, the Slick-Modal library is not contained in this extension. You have to provide it by your own - but no worry, that's easy. First you need to get the Slick-Modal library. If you haven't it yet, you can buy it here for less than $10. This library needs to be uploaded to your website. We create a directory like /fileadmin/Libraries/SlickModal/ and copy the hole files of the library into. Now you have to tell the Slick-Modal extension where this library files are located. This can be done by the two following TypoScript-Constants:
Now you're able to use Slick-Modals.