In Intellij, go to file > project structure (ctrl + alt + shift + s with keyboard shortcut) > Modules > Dependencies > click on the plus button > Jars and > select the Jar and click Ok > click Apply and Ok to close settings.
In Eclipse, Right click on your project > select Build Path > click on Configure
Build Path > click on Libraries and select Add External JARs > select the jar file > click Apply and Ok.
Add file named testproject-sdk.properties under resources folder with the content version=0.63.1 (or other version if you prefer).
Run Maven commands Clean > Compile > Package. You will see a Jar file under target in the project tree.
Or Gradle commands Clean > Build > Jar. You will see the Jar file under build > libs
In TestProject go to your project and click on Add a new Test > select Code test type > drag the Jar file to the upload area and click on Upload > click Next > provide (meaningful!) package name, you can add Description and Application as well > finish the wizard.