If you have external hard drive or usb stick memory and you want to format the data on it, you can do it from inside lubuntu, there is a tool for that.
On lubuntu you can use the gnome disk utility to format external hard drive (or internal) and other removable storage like usb stick, sd card, etc.
You don't have to install gnome disk utility, because it's already included on the lubuntu installation, to open gnome disk utility, click on lubuntu start menu > Preferences > Disks.
The gnome disk utility is a GUI program for formatting hard drives or storage devices, it's a good thing that this tool is a GUI so that anyone can use it specially for those who doesn't like command line.
And for those who loves command line/console so much, i believe you can use program called mkfs to format hard drive using command line.
Anyway this article is about formatting hard drive/usb stick/usb flash drive using gnome disk utility (disks) so here's screenshots of gnome disk utility to give you an idea of how it works.
To format with gnome disk utility, choose the storage device you want to format, and then click on the wheel/gear icon, select 'format partition' and then choose file system format type you want to use (NTFS, FAT, Ext4, etc) and then click format to start formatting.