How Do I Can Call Post Method From Direct From Url?

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PostgreSQL

WebAPI

EF6.0

Good Afternoon ,
I want to make web api , which will be in my existing " WEB FORM Application " and i want to GET , POST my data in database ( POSTGRESQL ).
First , when user click on my webapi url , it will ask for client certificate if its valid (till here done ) then user can GET and POST their data.
How could i call POST method , when valid user come on my api ?
If any one have answer reply me.
Thank you.