It is legal in UAE. You will have to open an account with a registered bank that offers such services in the UAE. There are many foriegn banks that sell share trading, eg saxo bank. These products often include trading in curencies along with equities, futures and options.
Yes Forex is legal in UAE, everybody is free to do forex trading. They just require a trading account which they can open with the help of banks who provide the trading account service. After an account opening, they can either use forex trading signals or any other software for making profitable trades.
There are so many online firms for forex trading. You can contact them . They will send u detailed mail which step by step process . To trade in forex.