ZK consists of several libraries (the JAR files). There are two alternatives to install them.

First, you can bundle them with your Web application. In other words, copy them to the WEB-INF/lib directory of your Web application. The benefit is that you can deploy your Web application to any Web server without configuring the Web server.

Second, you can install them to your Web or application server. In other words, copy them to the shared directory of the Web or application server (for Tomcat, it is shared/lib). The benefit is that all Web applications deployed to the server can use ZK without bundled with ZK libraries.