How to import packages from the external Library in Java?

I'm a n00b coder. I found an interesting library and trying to start toying with it. Which is not going great. This library is from 99' and uses JUnit (which I'm unfamiliar with) so there is a lot of confusing stuff. But it seems like the source of my failing even more elementary. Namely I have troubles importing packages.

This library has a test called StandardEvalTest.java. I moved to it to main Java directory and now I'm trying and failing to launch it using JUnit.

This package path org.pokersource.game.Deck goes directly from the directory where the test StandardEvalTest.java sits.

I also added the main java directory to the PATH environmental variable. Which as I assumed will allow import to locate the package.

None of those two things help. Also I was suspecting that maybe Deck.java and Deck.class are not enough and I have to do some work to create a package from it. But as far as I can say from Oracle doc the only thing needed is a package name in the header. Which seems to be present.

So I'm out of moves. Please help!

PS: Some additional info inspired by @Dhrubo 's answer:
The test I'm trying to run indeed sits in the main java folder of the library. (I moved it here hoping that when running from here it would be easier to find the package)

If I'm trying to compile the test instead of running it with JUnit he seem to fail to find JUnit classes and other JUnit related stuff.

[Oh OK I'm an idiot! Dont't mind me]

You should include the package while running StandardEvalTest.java as below

javac -cp [classpath] org.pokersource.game.StandardEvalTest.java

and run it from package root directory, I am assuming it is custom java file that you want to compile. You run directory should be parent of your package directory.

** I also see, you are trying to compile StandardEvalTest.java instead of Deck.java ... then check your StandardEvalTest.java file whether it exists in desired location.