As you can see the TringMe account page displays almost all the information you required to set up your widget.
1) User Id: This is your tringme id used in your Widget URL.
2) Phone Credits: By default, you will get 5 free credits which will entitle 5 mins calls for FREE. This is purely for testing the system. The new free minutes offer is yet to be launche

3)Website/Blog: Optional field
4) Phone : you need to select the country and put number in local number format without country code.
5) Gtalk ID: Put your google talk id. This will let you receive calls or voicemails if you set send my voicemails/calls option to Gtalk.
6) send my voicemails/calls option : You can select Phone & Email Gtalk / Email or Email only. If you select Phone, all calls will be termination to your phone number and respectively for other options.
7) Public Page is a personal widget page assigned by Tringme. you can give this page to your friend so that they can visit the page and call you.
8) Widget Code: this can be used on your favorite social bookmarking website, so people can call or leave a voicemail.
Now if you visit my Personal Widget Page (I am not sharing the url to avoid prank calls lol), you would see something like this:
Once you click on the Voicemail or Click to Call option, the widget immediately places the call to my destination number set in the account page. I pickup the call, you are connected. You can talk to me using your headphones.

Of course at this stage, Tringme is only available for Beta testers. However I am giving away 25 invites to start with.
I made a post at tipsity, for Tringme invites, if you need a invite please reply to this post: Tringme Invites Available
Besides this, Tringme is now offering Toll-Free solutions to Enterprise/Business users. I will make a seperate post to explain how TringMe Enterprise VOIP Solutions can bring down cost on your Toll-Free numbers. If you are interested in knowing further details, please contact ut.godmode(at)gmail.com. Please explain your requirements.