What things do you want to know? All the best distros have a manual or a wiki which will get you off to a good start, like
When you've installed, the user interfaces have their guides, accessible with F1, and their websites
Programs have their help and websites.
The mysterious command line (great when you get to know it) is best explained by the old but good RUTE:
Above all, try things out! So long as you always make a backup of a file before altering it, you can recover from any mistakes. Unlike James Bond, you can't make your computer explode from the keyboard!