Tell me the steps to do it
Hi @irshad.sabik18gfy , welcome to Thunkable! 
Be sure to check out our posts about How to ask Great Questions v2.0 and our Community Guidelines as you get started.
You can find more information about In-App Purchase Blocks with RevenueCat here: In-App Purchase Blocks (with RevenueCat) - Thunkable Docs
And we have some other posts using Stripe and Paypal:
Understanding Stripe API (App demo link below) - Tutorials and DIY Guides - Community (thunkable.com)