I’m not very familiar with Inkle, but if you have a ZIP file with the game inside you can go to the jam’s "Overview" page and click the button that says "Submit Your Project". This should take you to a page where you can set a title for your game and upload your game’s files to be downloaded. If not, it may ask you to submit something you’ve already uploaded to the site, so you can do the same process already mentioned but accessed by clicking on your account in the top right of the site, then "Upload New Project", after which you can return to the jam’s "Overview" page to select the project you wish to submit.