how to use my site address to login

Hello,

i have installed my wordpress blog using cpanel
https://icchurchborivali.org/b

this is my wordpress url https://icchurchborivali.org/b
this is my site url https://blog.icchurchborivali.org/

when i use my site url and click login i am taken to the dashboard and can work perfectly,
but when i click my blog name from my dashboard it takes me to my blog site url and i am logged out.
if i simply reload the page with wordpress url, i am logged in

please help me to use my site url

[snipped login & passwords]

thanks