How to pay using LifeSG?

Excuse me, could you please elaborate on the process of paying using LifeSG? I'm a bit unclear on the steps involved. Do I need to create an account first? And how do I go about adding funds to my LifeSG wallet? Also, are there any specific merchants that accept LifeSG as a payment method? Lastly, is there a limit to how much I can spend using LifeSG? Thank you for your time and assistance.