The easiest way to get started is to configure your IDE to use a recent Project Loom Early Access (EA) build and get familiar with using the java.lang.Thread API to create a virtual thread to execute some code. Virtual threads are just threads that are scheduled by the Java virtual machine rather than the operating system. Virtual threads are best suited to executing code that spends most of its time blocked, waiting for a data to arrive on a network socket or waiting for an element in queue for example.
Many applications won't use the Thread API directly but instead will use the java.util.concurrent.ExecutorService and Executors APIs. The Executors API has been updated with new factory methods for ExecutorServices that start a new thread for each task. Virtual threads are cheap enough that a new virtual thread can be created for each task, there should never be a need to pool virtual threads.
The following start starts a virtual thread to print a message. It invokes the join method to wait for the thread to terminate.