rm -rf "name_directory"
With the help of rm you will use the remove command; with -r you will select anything on a specified directory; and with -f you will force, omitting any rule or barrier of security so you must be careful because an rm -rf command could delete any important data from your disc so you will need admin permissions to execute that command but you will discover could be useful sometimes.
Also, note that when you need help with any command you can use the man command that will show you a manual for the command selected for example in this case you can write