You still seem to be confused!
As I said earlier (and pokedmund reiterated) there are NO EXAMS in either the CELTA or online TEFL courses, so in that respect there is nothing to prepare for.
As the name suggests, online TEFL courses are conducted online. You pay for the entire course upfront and work your way through the modules at your own pace. Everything you need to know to enable you to complete the exercises will be contained in the module, although you can always Google anything you would like more information on. You submit completed modules to your online tutor and he/she will provide you with feedback.
The CELTA (as pokedmund has explained) is a 120hr course conducted in the classroom. It comprises input sessions, teaching preparation, 6hrs assessed teaching practice and 4 written assignments. To find your nearest authorised centre, click on the following link and select a country and choose 'CELTA' as the award. See: http://cambridgeesol-centres.org/centre ... g/index.do
To enable us to give you more targeted advice, perhaps you could answer the following:
1. Are you a native English speaker? (I only ask because people have suggested TOEFL to you which, as Lucas explained, is the test that non-natives take).
2. Where are you based?
3. Where do you want to teach?
4. Do you want to teach full-time or just for one summer for example?