Procedure to install BHIM can be found @ http://www.npci.org.in/BHIM_Product_Overview.aspx
FAQ on BHIM can be found @ https://upi.npci.org.in/static/faq/en_US/
In order to activate we need to enter our debit card last six digits and Validity (Expiry) date of the card. In SBI and SBI group bank Maestro cards validity dates are not available.
To find the validity date First login to your internet banking account using https://www.onlinesbi.com/.
Then go to the e-services and chose ATM Card Services
In that, you can find ATM Card Limit/Channel/Usage Change.
Click and go to the ATM Card Limit/Channel/Usage Change.
In that, you can see the Card status and Expiry date.
Enter the expiry date and debit card last six digit number and activate your account.
Enjoy! Happy Banking!