Dear Mr. Prasad ,
You may pay tax online through www.NSDL .com .
provided you have net banking facility with your respective banker. ( facility for payment of statutory duties)
Secondly as far as CENVAT credit facility is concerned :
It is simply a input credit facility ( for the tax that you paid may it be through Electric Bill , Telephone Bill or even if you import any capital goods from abroad , a portion of the Custom duty is also eligible for having input tax credit provided such service or good must n be used exclusively for your output service .
you may also have the carryforward facility of CENVAT .
Input tax on Revenue Item is allowable to be deducted 100%
where as same on Capital Item is allowable only 50%.
balance 50 % to be adjusted in next financial year.
Regards ,
Debashis .