you can likely embed username and password by adding ?login=myusers&password=mypassword to the url, so:
https://www.example.com?login=myusers&password=mypassword
Note that some characters need to be escaped, e.g. if the username is an email address you need to replace @ with %40 and so on.
There are some URLEncode and URLdecode functions for that.
Also try to avoid hadcoding it and do not use with http, only for https:
http is plain visible in traffic
https: everybody that can extract the url has access to your site.
A better way is to login automatically using certificates.