What the Branded sending domain does is when you send an email it says that it is sent from your domain and not klaviyo
Go to Klaviyo page > click on you profile in the bottom left corner > settings > Account > Domains > Add
Select your root domain and select Dynamic > Write “send” in the sending domain >Select your Domain Host (where you bought your domain name) and you will get a guide on how to add DNS records
They will guide on how to get to the DNS record zone in your domain provider, then you gonna enter the values giving by klaviyo.
For the last value you can either write “@” or leve it blank both work
Hit save, once they've been added, go back to Klaviyo to verify them. It may take 24-48 hours for them to verify, but usually they work quicker than that.
If there are any issues, double check your records or contact me.