Card must already be partitioned for use in Windows, in which case the MBR (Master Boot Record) already present needs wiping.
If the card is plugged into a PC, you can use the DISKPART command to achieve this.
The procedure is explained and a how-to is shown here:
https://www.windowscentral.com/how-clean-and-format-storage-drive-using-diskpart-windows-10
Do not proceed past step 7 if you plan on using the card in an Amiga or WinUAE. Go directly to step 13.
Also, if you plan on using the card in WinUAE, ensure that WinUAE is 'run as administrator' before you try hdtoolbox again or you may run into problems.