Religious conversion

People who convert easily are very likely to go back as quickly as they came.. Today she likes you, she wants to be with you. Tomorrow if she discovers that she doesn't like you anymore, then.. ?? Are you prepared for all eventualities..

As the proverb goes:

A man (person) convinced against his will is of the same opinion still

You have to approach muslim priest and perform the marraige under Muslim law. The priest will give marraige certificate. Submit the same before the office of sub registrar (Assurance & Marraiges) nearest to your residence. To my knowledge it will take two months to complete all the formalities.