Oracle data access

I have an initial code for my application which access Oracle database. When I run app, I got error "Could not load file or assembly 'Oracle.DataAccess'  or one of its dependencies. An attempt was made to load a program with an incorrect format.  I search online here for solution:
http://stackoverflow.com/questions/15596834/could-not-load-file-or-assembly-oracle-dataaccess-or-one-of-its-dependencies

I have 2 questions:
1. The above link mentioned about run command like md or copy from within an administrator console. Where is it for "from within an administrator console" ?

2. The link also mentioned run gacutil if Visual Studio is installed. Where is gacutil and where to run the gacutil command?

Thanks.