If you want to propose a trade, select "Propose Trade" from your Team Page. Then we email the other manager with your offer, which also shows up on their team page.
To discuss other general issues, a number of options exist.
By going to the Managers page—listed under the League Info section of your league page—you can find the Yahoo! ID and email address of the other managers in your league, assuming they've chosen to make their contact information public.
When you've done that, you can send a manager an email, use their Yahoo! ID to communicate, or chat via Yahoo! Messenger.
If you'd like to contact a manager who doesn't list their contact info, try posting a message on the league message boards. This is also a great place to discuss Fantasy Basketball issues with the other members of your league.