How to change my app store password ?

Go to https://appleid.apple.com/, click 'Manage Your Apple ID' on the right-hand side of that page and log into your account. Then click on 'Password and Security' on the left-hand side of that page and then at the top of the right-hand side there should be a 'Change Password' option which you can click on.

I think that you should also be able to do it on your iPad by tapping on your account id in Settings > Store (Settings > iTunes & App Stores on iOS 6) and selecting View Apple ID on the popup, and then clicking on your id at the top of the next screen

Hi Medhataskar,

If you can't remember your Apple ID Password, or want to change it, use the password retrieval process at My Apple ID. Follow these steps to change your Apple ID Password:

1) Go to My Apple ID and click Reset your password.

2) On the next page, enter your Apple ID Name and click Next.

3) Authenticate by email or by answering the security question.

4) By following the emailed link or answering the security question, you'll be presented the option to reset your Apple ID password.