Get Current logged in user from sharepoint to Power Virtual Agent

We are creating a chat bot using Power virtual agent and using it as iframe in spfx. We need to get the SharePoint current logged in user in that power virtual agent chatbot window.
We have configured SSO option and added that as custom script in the sharepoint.
https://learn.microsoft.com/en-us/power-virtual-agents/configure-sso
By this everytime I open the sharpeoint page where the bot got deployed it automatically populate one window to get the username and password and logged into the power virtual agent chatbot.
How can we bypass the auto populate window? how can my Power virtual agent will recognize the user without prompting the login window option.
pls advise?