You need to activate the package in advance before using it(prepaid). After every session of using the internet, it will update you with your credit status along with the remaining data transfer limit for the package bucket.
To activate/get 10mb/30rs bucket every time, simply send a message (blank message) to 3282 and warid telecom – Pakistan will respond you with the confirmation that the bucket has been added to your account like this:
GPRS bucket of 10mb has been successfully credited to your account
You can add multiple buckets at a time too.