In Minecraft Java Edition, players can either jump into a world on their own and explore it, or they can join their friends in a multiplayer world and play together.

There are three ways to play multiplayer in "Minecraft: Java Edition:" through an online server, a LAN server, or a "Minecraft Realms" server.

From this point on, as long as you have the server open on your PC, any player should be able to join after performing these last steps: Open Minecraft: Java Edition. Go to Multiplayer > Add Server.