if you have a purchased Minecraft account, do the following things:
1. Open up the Minecraft Launcher
2. Click "Play" at the bottom of the launcher
3. Wait for the game to load
4. Once the game is loaded, click the "Multiplayer" button.
5. Go to "Direct Connect" at the bottom of the Multiplayer screen and click on it
6. In the empty box, type play.wynncraft.net
7. Connect to server
If you don't own a minecraft account you can buy one here https://minecraft.net