Manage partitions - there you first have to choose the device (flashdrive, hdd, ...) choose your device

Then you can change the number of partitions - or just use the pre-defined partition table,
double klick on the entries (e.g. filesystem, label, ...) and the changes get indicated properly.
If you are happy with your new layout just press the apply button (green tick) and the tool will do the rest for you...