How to connect a Oracle DB?

Question

Hello,
I searched the forum and possible articles. I read all articles but actually I understand nothing. I still dont know how to connect.

1. Is this possible to connect a oracle db, without installing a program? (Like Oracle Data Provider for .NET)

But, I installed  "ODAC 11.2 Release 3 and Oracle Developer Tools for Visual Studio (11.2.0.2.1)" from Oracle web side. Then accordinf this article --> http://www.c-sharpcorner.com/UploadFile/nipuntomar/4749/

I want to add;
using Oracle.DataAccess.Client;
line to my code but VS is not recognize this line.

Actually I couldnt find an article that explaining step by step.

Simply, How can I do that? Is this possible to connect only a single connection string?