This is the name of the application, it must be alphanumeric only.
The website for the application, github links are perfectly acceptable
The License the application is released under, this can usually be found on the website or on github.
A short description for the application, either taken from the website, github, wikipedia. Keep it short to a single paragraph.
Icon for the application, should be 250 x 250px with a transparent background. PNG or SVG files
The colour of the tile, if your icon is dark you should probably pick "light", and vice versa
After you have filled in the form a zip file will be generated, you will need to fork the Heimdall-Apps repository, extract your zip, merge your changes and finally create a pull request... don't worry, it's not as hard as it sounds.