So you make music. Please keep in mind that notype.com is a collective of many labels. Some are active, others aren’t. They are all managed by different folk.
In order to submit a demo, go to any label’s page and check if there is a demo policy. If so, that’s where you’ll find the instructions. Good luck! :)
If the label you’re interested in does not show a demo policy, it probably means it doesn’t accept them at the time. :(