Thanks sdayman. To proceed with the advance mode installation:
1) As I'm still with my existing domain registrar, do I need to update my A record with DH's server before installation or I can do it later? Also, would like to know which server to choose as I have been given 3 of them... first, second or third one?
2) Before clicking "Install it for me now", as I'll be using the domain rather than subdomain, eg www.example.com, do I need to fill up the blank space after the "/". E.g. www.example.com / XXXXXX. And may I know what's the blank for?