Audacity is an excellent soundn editing tool that lets you do wonders. For example reducing background noise from dialgue and interviews.
This is a simple tutorial from Audacity website, which helps you do just that, reduce background noise, after your recording is made. But there is no substitute for ensuring the romaval of noise before recording. For example, switch off the AC, Fans, anything else that makes noise, shut the doors and windows, take a microphone close the the speaker etc.
How to remove noise with Audacity