How do I tell a client to set up Outlook on their desktop when switching hosts?

hi all,

i have a client that uses outlook for their email client. they are going live and need to switch email hosting servers. how do i tell the client to re-configure their outlook so that they seamlessly receive their email on their desktop and mobile devices?

how do i also tell the client to back up all their outlook files before the transfer of email servers begins?

i have a ton of support links but don’t know which one is the best/most simple to send to a client with very little tech knowledge.

can someone help please.

thanks.