Before posting, please make sure that this hasn't already been reported by someone else.
Please make a list of steps to reproduce the problem (ideally from a fresh Wurst installation):
If applicable, add screenshots, videos or other files to help explain the problem.
Please find your crash report file at "%appdata%/.minecraft/crash-reports", open the file in a text editor and copy-paste its content below.
(crash report goes here)
Please note: If the game did not crash, please hold down F3+C for 10 seconds to generate a crash report. Even when a bug doesn't cause the game to crash, this file still contains useful information that can help us to find and fix the problem. Because of this, please always include a crash report.
This is too vague to be useful as a bug report. Please add the necessary details, like exact versions and a crash report.
Also make sure you actually followed the installation tutorial. Most issues of this kind are caused by improper installation. https://www.wurstclient.net/tutorials/how-to-install/