Go to the SharePoint Site Contents page:
Select the page and add your report:
Click the gear icon on the right, and then Edit page:
Under Categories<- Media and Content. Parts<- Content Editor, and Add:
Select new content. From the menu, Format Text<- Edit Source:
In the Edit Source window, paste your iFrame code in HTML Source, and then select OK:
Page, <-Stop Editing:
For more information on Power Bi, check the following Power Bi Training