Uber has added Paytm option to its desktop sign up site (Click on Sign up here) or mobile site as well, just you have to select the country (India +91) properly to appear paytm option.
Uber will set you up with Paytm Wallet using the phone number and email you have above. If you have an existing wallet, Uber will connect with it using OTP method.
OTP method: Uber/paytm will you send you an one time password on your mobile/email which must be entered to your uber app in order to authenticate paytm in with uber.
How to get promocode for uber signup? (Read here: How to know if promocode is applied?)
You will need to enter promocode in order to get 1 free ride from your referrer. If nobody referred you, Uber Account sign up with Latest Promo Code.
Update(July 16th 2015):
Uber has updated its payment system and brought back the credit card option in recent upgrade in android app and desktop login page. Earlier Uber used to show(refer above screenshot) paytm wallet option on desktop site not its back to normal and asking for credit card details.
The good part of new credit card payment option is, uber will not be able to take payment without your consent each time you book. Every time you have to enter security digit, and i-pin, OTP to authenticate your payment. This step will protect your money and card from access payment or illegal payment or any fraud.
Card security code
A card security code (CSC), (also called card verification data, card verification number, card verification value, card verification value code, card verification code, verification code (V-code or V code), card code verification, or signature panel code (SPC) are different terms for a security feature for "card not present" payment card transactions instituted to reduce the incidence of credit card fraud.
How to use uber on feature phone with browser? No apps required.
Sign up here on mobile site of uber: Desktop/mobile site for sign up
Book your ride on your mobile browser: How to book uber cab ride using mobile browser