Visit Magic Eden

To buy:

Find a Bee or Queen listed in HXD

Tap on the + sign in the upper right corner 

Then tap the red button in the lower right area that says "Buy 1 item for xxx HXD"

To sell:

On Magic Eden, navigate to the collection for the item you wish to sell, choose your asset, choose list, change the currency from SOL to HXD (see screen shot below)