Cannot use Mac Mail to send email via my two gmail accounts (e.g. iPhotos)

Gmail I cannot configure Apple email on my MacBook Pro to allow me to send iPhotos (for example) via one of my two gmail accounts. I do not normally use Mac mail but I'm stuck with it as part of my software.

One message, for example, claims "Gmail not online" when in fact it is.

I have put in the passwords in both the Account tab and the Advanced tab.

Would appreciate your help. Thanks!