Your broker should provide you three features in order to use the platform: Your account number, your password and the server. First time you login, go to File -> Open an Account and check the connection of your server on the "Ping" platform (make your it is not 0ms) and then login with the existing account. Same details will be required if you log via the app or the web platform
In order to add an indicator copy the file and then go to File -> Open Data Folder -> MQL4 and then paste it under Indicators. Then restart your platform and the indicator should be under the Navigator window. From there just drag and drop it an your chart.
In order to add an Expert Advisor on your MetaTrader, copy the file and then go to File -> Open Data Folder -> MQL4 and then paste it under Expert Advisors. If you have been provided other files you should be given instructions for them as well. Typically a file that has a .dll extension would go to the "Library" folder. Restart your platform and the expert should be under the Navigator window. From there just drag and drop it an your chart making sure you enable automated trading. After that you need to go to Tools -> Options -> Expert Advisors and enable Automated Trading and DLL's. If installed correctly, you should see a smiley face on your chart.