How to implement single sign on (SAML) concept in ASP.NET

Hi ,
i want to implement single sign on(SAML) concept in my project.

i have created a simple asp.net web site, from this asp.net site i want to call another third party site(ArcGis tool develped online) without login again to that third party portal.

i have below the details of that third party portal(which is ArgGis Web Builder portal).
ApplicationId, tokenId, ClientId.

i tried to use the token and tried to redirect from asp.net but it's prompting me to login again there and after providing details it's redirecting successfully but i want to login there without prompting login.

can any one plz give any idea how do i call non asp.net site from my asp.net site. i can created same login and password for both the site(My Asp.net site and ArcGis portal) but don't know how do i pass user credentials to that portal(ArcGis) so that it will not prompt any credentials.

it's basically user want to login in asp.net site but can visit to another portal without login there.

let me know if i need to create any service from asp.net site , if then how do create service or is it possible to use active directory with AD login.