"Now that" - What does this mean?

English as a Second Language English Vocabulary, Grammar and Idioms
1

Hello,
Please look at the following sentence. I have just read it in a letter:
‘‘Now that I am able to write to you…’’
I wonder what ‘‘now that’’ means because I can’t find them in all my dictionaries.

2

Hi,

This means: ‘Since the moment has now arrived when I am able…’

Alan