How do I connect a domain that my client purchased?

Hello,

I have made a website for my client/friend which is now ready to be connected to a domain he purchased via GoDaddy.

What is the best way to connect the domain to the website without having to log into his GoDaddy account (I think he would give me access for this purpose but would rather not ask)? I could give him instructions to do it himself but wanted to know if there was a better way as he may struggle doing it.

Thanks in advance!