If you have downloaded a .rar or .zip file containing this indicator, follow these steps to install it on MetaTrader: What Is a Bid-Ask Spread, and How Does It Work in Trading?
Standard MT4 charts often display only the (the price at which you sell) by default. A custom "Bid Ask Line" indicator adds a secondary horizontal line to visually represent the Ask line (the price at which you buy). The gap between these two lines is the spread , which represents the transaction cost of the trade. How to Use the Indicator