(Changed Title to reflect question more clearly)

Mobile office basically works over GPRS, first of all you need to know following things from your customer care:
APN ie. Access POINT
IP address and
PORT number.

Now in your windows mobile you have to configure it.. though for me still it is little confusing but may be I can help you..

1.
Goto > Start --> Settings --> Connections ---> Connections
It will show your current configured connections, depending upon y0ur settings, I see MY ISP connection with option to "Add a new Modem Connection".

2.
Open it and give  any name and select MODEM as "Cellular Line (GPRS)".
Now Press Next

3.
It will ask for APN, give APM provided by Customer Care.
Now Press Next

4.
 You will be asked to provide username  / password etc.. Leave it all blank.
Now Press ADVANCED :
If customer care gave you IP address  then Select "Use specific IP address" and enter IP address there, also enable Software compression and IP header compression (not compulsory but should improve performance).

else if no IP address provided by customer care or they don't know IP address for mobile office then just let it as it is ie. "Use server assigned IP address".

Press OK and then Press FINISH.

.....
5.
Now again PRESS "Advanced" where it shows all connection list and Press "Select Networks"

6.
Now Under "Program that automatically connect to internet should connect using: "
Select the account name under which we just configured our modem connection few second ago.

Press "OK" and again "OK" and you are done.

Try your browser in your phone and it should work..

If not then try asking here..

For your convenience..
APN for airtel mobile office is : airtelgprs.com

Try that and let me know!