How to buy Mail Lite

How to buy Mail Lite

So I went through help topics etc and I still got no idea how can I change from free to lite.

Pricing page (https://www.zoho.com/mail/zohomail-pricing.html?src=hd)
got all the paid options listed , but the buttons redirects to my inbox.

When I click on profile picture, the only 'upgrade' button is under 'used space' category and all I can buy there is additional capacity for my account with a totally different prices (see screenshots).

So, how can I actually, step-by-step, buy Mail Lite instead of extra storage?