The steps you'll want to take will depend on what you are trying to achieve. 

To change the email address you use to log into Front, you will need to follow the instructions here in our Help Center.

To change the address you use to send and receive emails in Front, you will want to disconnect your current email channel from your inbox, and reconnect the new one. 

To do this, go to Settings > Inbox > select inbox > Channels > select > remove channel. Then, select "add new channel" and follow the steps to connect your new email address.