Sure. You will get emailed Wanted and Offered posts, browse through them, if anything offered takes you fancy, reply to the person saying you're interested, ask if the item is still available and (I always find this helps) offer an idea of how soon you can collect it. Add your phone number at the end of the message but don't actively ask them to call you as some people find this cheeky! Please and thank you's go without question (surprising how many people don't ask politely though!)
If they email/call you back offering it to you, then take their address and arrange a time to collect.
Place a wanted ad by going to the freecycle group you're on, and clicking the "post" tab. Always write the title like "Wanted: Table" no extra info. Then people will respond to you as above.
Place an offered ad in teh same way but always put a location in brackets at the end of the title, as it saves people just emailing to ask how far away from them you are.
Then, after you have given/taken, write a Recieved or Taken post to let people know stuff is gone, and thank the giver/taker in the bod of the post.
HTH!