I'm goging to explain how to connect oracle database using sql server management studio

follow below process -

Control Panel -> Administrative Tools -> Click on ODBC data sources(64)

Click on system DSN tab and click on Add button then window will be open As 

Here select Oracle in OraClient11g_Home1 and click on finish button then window will open As-

Here if you will not get OraClient11g_Home1 then click on this Link

Here provide your Oracle database details and Data Source Name as above

Click on test Connection Button then window will be open As-

Provide oracle database password and click on OK button then message will show Connection Successful.

Process to Connect with Sql server management Studio

Open management studio and Login then window will show As –

Here Click on Server Object -> Right Click on Linked Server -> Click on New Linked Server then window will open As-

Linked Server -> Enter Name  as I have Enter MMS

Provider -> select Microsoft OLEDB Provider for ODBC Driver

Product Name -> Here Specify Any Name I have specify MMS

Data Source -> Here Enter Data source Name Same as created Above

Now Click on Security Tab then window will open As-

Here check radio button as above screen

Provide Oracle User Id and password and click on ok button

Your linked server will be created.