Go there NOT using Firefox. Firefox browser unfortunately doesn't work for your first upload to tiddlyspot (after that it does work). So use e.g Chrome or Safari when you want to create a new TiddlySpot.
You'll see tiddler $:/EmptyStart
So, to create a new tiddlyspot you do't have to actually go to
tiddlyspot.com. Instead you go to quicktiddlyspot and fill in the fields. It has a clipped iframe so it creates the new tspot when you (there) click "Create".
Then continue to fill in more info and upload it to that just created tiddlyspot.... and then click the link to go there.
In the new tiddlyspot you'll once again be met by this $:/EmptyStart where you can tweak and then delete that tiddler as you don't need it anymore.
It's more practical than pretty. Just like my aunt Martha.
<:-)