when im debugging my module in visual studio; how do i step into dotnetnuke function, for example

Localization.GetString ?
i need this cos in dotnetnuke scheduler localization.getstring dosnt return translated word, even though i created http context by following some tutorial. 

I'm not sure you understood my question. I can step into fuctions of my module. I need to step into function that is part of dotnetnuke.dll, so that I can see why it's not returning expected value.

 I installed dotnetnuke .pdb files, i also have dotnetnuke source files, but im not sure how do i tell debugger it can step into function, and where does it look for source files. I think i need dotnetnuke.dll that was built using "debug" flag?

And with the help of stepping into source code of dnn functions I found out why localization.getsttring wasnt working in scheduled job. I had to do this:

objPortalInfo = CType(arrPortals(i), Entities.Portals.PortalInfo)

'this makes translations into local language work in http context free enviroment!!!
Dim objPortalSettings As New PortalSettings(objPortalInfo.PortalID)
HttpContext.Current.Items("PortalSettings") = objPortalSettings
System.Threading.Thread.CurrentThread.CurrentCulture = New System.Globalization.CultureInfo(objPortalSettings.CultureCode)
System.Threading.Thread.CurrentThread.CurrentUICulture = New System.Globalization.CultureInfo(objPortalSettings.CultureCode)