You didn't mentioned what version of Visual Studio 2012 you have installed, but i do believe that you use Express version. Neverthless...
I'd suggest to download and install
MICROSOFT® REPORT VIEWER 2012 RUNTIME[
^]
Now:
1. go to the form designer
2. right click on the toolbox then choose
add items
3. browse for the
Microsoft.ReportViewer.WinForms.dll
(default location:
%windir%\assembly\GAC_MSIL\Microsoft.ReportViewer.WinForms\10.0.0.0__xxxxxx\
)
A report viewer's controls should appear in the toolbox.
Good luck!