Hello @safeerind we are happy you've decided to support us with Windy Premium!
You have two options. You can subscribe via desktop or App/Google Store. You will find Windy Premium in Menu. No matter on which platform you purchase it, you will have access to Windy Premium on all platforms.
Here is more info about Windy Premium
https://community.windy.com/topic/11552/we-are-launching-windy-premium-even-better-forecast-for-just-price-of-a-lunch?_=1590995129778
In case you have troubles to access Windy Premium once you purchase it
https://community.windy.com/topic/11832/what-to-do-if-you-can-t-access-your-windy-premium-features?_=1590995129781