push button to switch arduino coding

i want to use two different codes in one arduino plz any one help.what i want is (arduino start then a message is written on lcd press first push button for this coding and press second push button for this coding, if first push button is press it will run the first program and vice versa)

Put the code for what you run in separate functions and call the appropriate function when you want to run it after the user makes a choice.

Do you know how to read user input from a switch and interpret it ?

It is not clear from your description whether the user will be able to change between one and the other whilst running or whether it is a one off choice at the start.