How to reformat SSD

Open launchpad, click the "Other" folder and select "Disk Utility" (in the red box in the attached image),

and choose your external drive from the sidebar. Then, from the top bar, select erase. It will pull up a window with numerous options. If you just plan to use it for storage, just leave everything at the defaults and click erase. A pop up will appear asking you if you are sure. Tell its to go ahead and erase. It'll load for a minute or two and then, Presto! Your disk is erased!