- Touch the Launcher button on the Home screen.
- Find the 3G hotspot mobile button
- Tap the 3G Mobile Hotspot check box and enter a password.
- Touch the OK button and save settings.
- When the 3G hotspot is active, a Mobile Hotspot Service status icon appears.
- To turn off the 3G hotspot, open the 3G Mobile Hotspot app and remove the green check mark.
On my phone is it slightly different (Android 2.2):
1. Press the menu button (outside the screen),
2. Tap "Settings"
3. Tap "Wireless & networks"
4. Tap "Tethering & portable hotspot"
5. Tap "Portable Wi-Fi hotspot"
There is also a "Portable i-Fi hotspot settings" menu there to choose the hotspot name and password.
you can also check the tutorial in here http://howtonetworks.net/how-to-turn-your-android-phone-into-a-wi-fi-hotspot
thanks.