I'm confused that this even compiles, I guess all the extra brackets you added trick the compiler in some way. You can't just pass other parameter types to a function than those it expects in c++!
If you check the documentation - the first parameter it wants is a 'video::ITexture *' and not a string.
Irrlicht comes with examples (check the examples folder). You can open a project file which will build them all. If you use an IDE like VisualStudio or C::B you can search for a text over all files in the solution with ctrl+shift+f. Search for "addImage" and you will find several examples (04,05,11,12,16,17 and 21) which all can show you how to use that function correctly.