You can try several different methods:   Technical analysis: Technical analysis involves reviewing charts or historical data to predict how the currency will move based on past events. You can usually obtain charts from your broker or use a popular platform like Metatrader 4.  Fundamental analysis: This type of analysis involves looking at a country's economic fundamentals and using this information to influence your trading decisions.  Sentiment analysis: This kind of analysis is largely subjective. Essentially you try to analyze the mood of the market to figure out if it's "bearish" or "bullish." While you can't always put your finger on market sentiment, you can often make a good guess that can influence your trades. Depending on your broker's policies, you can invest a little bit of money but still, make big trades.  For example, if you want to trade 100,000 units at a margin of one percent, your broker will require you to put $1,000 cash in an account as security. Your gains and losses will either add to the account or deduct from its value. For this reason, a good general rule is to invest only two percent of your cash in a particular currency pair. You can place different kinds of orders:   Market orders: With a market order, you instruct your broker to execute your buy/sell at the current market rate.  Limit orders: These orders instruct your broker to execute a trade at a specific price. For instance, you can buy currency when it reaches a certain price or sells currency if it lowers to a particular price.  Stop orders: A stop order is a choice to buy currency above the current market price (in anticipation that its value will increase) or to sell currency below the current market price to cut your losses. Above all, don't get emotional. The forex market is volatile, and you will see a lot of ups and downs. What matters is to continue doing your research and sticking with your strategy. Eventually, you will see profits.

TL;DR in Indonesian:
Analisis pasarnya. Tentukan margin Anda. Tempatkan order Anda. Amati profit dan kerugian Anda.