First, download a modloader and then download VoxelMap. Move the downloaded file to the mods folder and everything will be installed completely when you start the game. If Minecraft crashes, it is often because the installed mods are not compatible with each other. In addition, it can be due to the game versions, for example, if you have downloaded and installed the VoxelMap and the API for different versions. In such unfavorable constellations black screens, errors, and game crashes can always occur. This is no reason to panic because you can reinstall everything. By the way, the installation also works if you use the Tlauncher instead of the normal Minecraft launcher.