If it Lehin manhwa then you make an account and buy coins or you can buy them frok the bookstore you also have the option to order from amazon.
What type of manga are you trying to buy? English, Japanese or another language? Any specific genre? Physical or digital?
Amazon- wide variety of manga digital or physical
Sublime- BL, digital or physical
June- BL, digital or physical
Renta- variety of manga mostly shoujo and BL, online only (?)
For webtoons (online only)- Lezhin and Tappy Toon
Lezhin
I want to know where do you buy manga to support the mangaka? Any reccomendations? Thanks