I thought it was in the tutorial popups, so sorry about that if it isn't! Immediately after the intro cutscene ends, you talk to the character to your south to trigger another tutorial, where you are able to put your tools in your inventory. Seeds are under regular items, tools under key items. You use the hoe to till the ground, then you can plant a seed in the tilled soil. Like I said, all that should have been in the tutorial boxes, so if it didn't pop up, that's a problem that I wasn't aware of. I'll look more closely at the browser version now, presuming that's the version you played.
Thank you for the feedback!