Help Drawing objects in CBot

Hi All,

Making the switch from MQL5 to CAglo and having issues with the basics.

I'm trying to get a CBot to put an up arrow at the high price of the last candle. 

Chart.DrawIcon(unique_name, ChartIconType.UpArrow, 1, Bars.HighPrices.Last(1), Color.Red);

Complies withour error, but nothing comes up on chart. I'm sure it's something silly I've missed. Any help would be appreciated.

Thanks