good place to look for is the Pega help : https://pdn.pega.com/sites/pdn.pega.com/files/help_v719/procomhelpmain.htm#basics/portal/userPortalsAbout/aboutCompositePortals.htm

Or enroll for the UI specialist course on PegaAcademy

Or if you feel comfortable, take a look at pyCaseManager7 portal (which is a composite portal) and do a save-as to start working you way in.

Thanks for reference information

Is there any video learning also avalable for the same?

https://pdn.pega.com/pegatube and then search for composite or portal

Thanks ☺