These steps are for MT5 on desktop. Menus differ in the web and mobile versions.
In the Trade tab, right-click the position.
Choose Trailing Stop.
Pick a distance, or choose Set custom level to enter your own.
Once the trade is in profit by that distance, MT5 places a Stop Loss and moves it as the price moves in your favour. It doesn't move back if the price turns.
Things to know:
A trailing stop runs in your MT5 platform, not on our server. If you close MT5, it stops moving, but any Stop Loss it has already set stays in place.
You can set one trailing stop per position or pending order.
Risk warning: CFDs are complex instruments and come with a high risk of losing money rapidly due to leverage. Only trade with money you can afford to lose.