I'm working on a project that requires Gradle integration. I've never used Gradle before, but I would like to add a .jar file as an external library. I copy and pasted the file into my main project directory and added it as a library by right clicking on it and choosing "add as library". I also added it to my classpath whenever IntelliJ highlighted any imports as an error. However, when I tried to build my project, I got errors saying "Grade: error: package X does not exist" and "Gradle: error: cannot find symbol class Y", where X and Y are packages and classes in the library. When I open the Gradle tool window and click on the refresh button, all references to the added library become errors, and I have to readd the library to my classpath. Doing this and recompiling still doesn't make it work, though. What do I have to do to get Gradle to accept the new library and to compile it correctly?