If you follow that link, and click where it says "tools" it will tell you exactly what you need in order to harvest it. You can even click where it says the name of the tool to find where you can buy it and how much it costs. You need your job to be "botanist" which means you need to have a hatchet equipped in your primary weapon slot. You can buy the "weathered hatchet" fairly cheap from an NPC.
So to make it clear, in order to harvest this item you need a hatchet and a scythe. Once you have these items equipped you can search around for sparkles in the grass and you will get the option to "harvest" them. I hope that helps.