Is there a tip or trick I need to know in order to buy HECO coins on my  metamask.  I have bought coins before but it won't show bnb in the actual slot to purchase the bnb coins.  I have the HECO network added to my metamask in the iphone.  If someone has bought Heco coins already please tell me the easiest way to do it.  Lately I haven't been able to get the heco and other network coins.  Maybe I am just not seeing something simple? I can't just buy them like other coins with the bnb already in my metamask.  thank you