Hi,
Did you selected
"Management Tools" option (checkbox) during installation? You need to select this option in order to install
SQL Server Management Studio.
Alternatively, you can download
SQL Server Management Studio installation media from here:
Microsoft® SQL Server® 2008 R2 SP2 - Express Edition[
^]
(press [Download] button and select "SQLManagementStudio_x64_ENU.exe" (64-bit) or "SQLManagementStudio_x86_ENU.exe" (32-bit) from the list.