As David said, just adding to that, whenever you want to add a portlet like the way you mentioned, first see that Page Layout that is being used by that project or that specific type of projects or any investments.
Project Default Layout is one of those Page Layouts that comes out of the box, you may be using some custom ones also. So that is why I mentioned to get the Page Layout first.
All the Page Layouts are basically one kind of portlet page. So you have to find then under Administration --> Studio --> Portlet Pages and then as David said,
Open it, go to Tabs and find the Dashboard tab
Go to Content and then Add!!!
You're all set, Cheers!