LONG (buy then sell) position :

A long position is simply one in which a trader buys a currency at one price and aims to sell it later at a higher price. In this scenario, the investor benefits from a rising market.

You as a trader should take a long position if you expect a currency to strengthen/rise/appreciate.

SHORT (sell then buy) position :

A short position is one in which the trader sells a currency in anticipation that it will depreciate. In this scenario, the investor benefits from a declining market

You as a trader should take a short position if you expect a currency to weaken/fall/depreciate.

STOP LOSS ORDER

A stop loss order ensures a particular position is automatically liquidated at a predetermined price in order to limit potential losses should the market move against an investor's position

Here is an example that will help you with exit target and exit stop-loss levels:

if you open a long position on a currency pair at 1.2000, your exit target should be at a higher level, for example 1.2020, and your exit stop-loss at a lower level, for example 1.1980.

if you open a short position on a currency pair at 1.2000, your exit target should be at a lower level, for example 1.1980, and your exit stop-loss at a higher level 1.2020.

If you want to buy above the current price you can use stop buy, if you want to sell below the current price you can use stop sell.

LIMIT ORDER

A limit order is an order to buy below the current price, or sell above the current price. For example, if EUR/USD is trading at 1.2952 / 55 and you believe that price is expensive, you could place a limit order to buy at 1.2945. If executed, this will give you a long position in EUR/USD at 1.2945, which is 11 pips better than if you had just bought EUR/USD with a market order.

In a limit order, the trader not only specifies the currency he wants to buy or sell and the number of contracts, but also at which price he wants to do so; in other words, a limit is an order to buy or sell at a specified price or better.

If you want to buy below the current price you can use limit buy, if you want to sell above the current price you can use limit sell

MARGIN

Margin is a performance bond, or good faith deposit, to ensure against trading losses. The margin requirement allows you to hold a position much larger than your actual account value. Trading platform performs automatic pre-trade checks for margin availability, and will only execute the trade if you have sufficient margin funds in your account. It also calculates the funds needed for current positions and displays this information to you in real-time. In the event that funds in your account fall below margin requirements, your newest open positions will be closed. This prevents your account from ever falling below the available equity even in a highly volatile, fast moving market

As a general rule, a position is kept open until one of the following occurs: 1) realization of sufficient profits from a position; 2) the specified stop-loss is triggered; 3) another position that has a better potential appears and you need these funds.

If the equity balance in your account falls below the margin requirement, a margin call will be generated. In the event that an account exceeds its maximum allowable leverage, some or all open positions will be liquidated immediately.