Click to my name (for example here @Nagash [ Ahh first time I’ve tagged myself ] , or one of my comment above) and you’ll see a Message icon like this (then you can start typing):
( Yes @Meliodas, you are a star now! )
Another way:
Click to your profile image above - upper corner of the site -, then you’ll find a mini 
icon. Click on it then you’ll find yourselfe in your Inbox. Start writeing a new message and tag my name (Add user > Nagash).
(I think, my direct link will lead you to the right page even on your phone. Dunno.)
Congratulation,
you’ve stepped on the path of your evolution. 
( Anyway, Sitri is a perfect Guy if you want to get a grill. I can advice to start working with Him. My latest - and first - experience with Him was fantastic. )