adobe photoshop cs2

By globe do you mean earth?
or do you just mean a generic globe circle like shape?
Are you wanting the 3D quality of the globe to be present?
Do you need the text to wrap around the globe?

ok i am a newbie to photoshop. Please tell me what tool to use to write the text  

ok now tell me how can i wrap the text around the globe.

that will be a very in depth multi-step process. May I suggest going to photoshop tutorial websites for this?  These tutorial sites can provide tips on how to accomplish a variety of effects. then you can use multiple tutorials to create the overall effect you desire. This will take some time in training/experience to do this and produce something visually very nice.

Photoshop is a very rich program. There are photoshop pro's that have used the product for YEARS, and still do not know how to use every feature and photoshop trick.

http://www.spoono.com/photoshop/tutorials/
This site is one of MANY you can browse through.

ok i activated the text tag with t and it showed me  a toolbar with a drop down for fonts etc but how am i to write...i tried with keyboard(not possible) with what other tag can i write

alternatively, here are some tutorials that may or may not produce the results you are looking for.

http://www.photoshopsupport.com/tutorials/jennifer/text-wrap.html
http://freephotoshopguides.com/text-effects/wrap-text-around-an-object-adobe-photoshop-tutorials/

first off, I hope you aren't set on creating something very visually stunning on your first try with photoshop. It's just not going to happen. Trust me, everyone fails miserably on their first fight with photoshop.

now as for you not being able to create text. Make sure you are on a layer that isn't locked for editing.

You may benefit from going through some basic photoshop training tutorials/programs to gain an understanding of all the basic features and the menu layout.