How to increase maximum_input_time ?

Hi ! when installing OPIGNO, I've got a message that my current set maximum_input_time of 60 is a required minimum that I may increase to 120. I cannot find php.ini file in which I can change the max _input_time value ....Could you tell me where it is ? Also, it is said that I may add a new line ini_set in settings.php. In that case, could you tell me what code to add and where ? thanks !