Step by step:
Go to your joomlabackend / JooDatabase
Define name of destinationtable
Choose and upload your spreadsheet file
If csv - set field delimeter and text enclosure
Set radiobutton if you want columnnames in the first line
Done (with first step)
You ask yourself: why can´t i see a new database at my jood-bbackend after my import?
Simple answer: because your not fineshed yet ...
Klick "new" (joomlabackend / Joodabase)
Define name of your db like "my little" db or what ever
Choose main table in dropdown (yippie, you just found your importet stuff, right?)
Depending on what structure (main table) you used for importing your data you´ll find it here ... match spreadsheetdata and template here
read also what Dirk wrote about mysql