You can use Bootgen in GUI mode in the Vitis IDE for simple boot image creation, or in command-line mode for more complex boot images. You can install Bootgen from the Xilinx Unified Installer.
After you install Vitis with Bootgen, you can start and use the tool from the Vitis IDE option that contains the most common actions for rapid development and experimentation, or from the XSCT.
The command-line option provides many more options for creating a boot image. See Using Bootgen Options on the Command Line for more information.