Dollar Costing Averaging is a technique used to spread the cost of an asset, effectively averaging out the cost that you have bought an asset at. It can also be very useful when a position has slipped into the red. Increasing your position size with DCA will also reduce the negative % the position currently sits at. clicking 'Actions' and then selecting 'DCA Position'
DCA can be found buy expanding the information about a position with the + clicking 'Actions' and then selecting 'DCA Position' as shown below
Once you have selected 'DCA Position' you will see the below:
Multiplier - This says how many times you want to increase your position size. For example you hold a position worth 0.1 BTC and select 2 in the multiplier, Apex will place and order for 0.2 BTC
Order Type - Choose whether Apex places a limit or Market order
Price - Input the price in which you want the limit order placed