First of all please download MT4 for Android from Google Play
After installing and launching MT4 you will need to choose "Login with existing account". Next, you will need to choose a trading server. In the "Enter company or server name" type forexs. Having done this you will see two servers in the list: "ForexServer-Demo" and "ForexServer-Real". In order to login to your demo account please choose the "ForexServer-Demo" server. In order to login to your real trading account please choose the "ForexServer-Real" server.
After the server is chosen you will move to the next step. Login with the account number and password that you use to login to your desktop application. Press the "Login" button and start trading.