Website
First login to the Company Admin Area. If you are not a company admin, you will not see Login to Company Admin Area.
On the menu, go to Issue Library. Select Import New Issues to upload your spreadsheet.
There you go.
Note: If all items are displayed in green like the above, the import is good to go. If there should be any errors, e.g. a duplicated item, the system would highlight them in red. In those case you may want to modify the spreadsheet to proceed again.