The steps to create a new linked server to access Oracle data from SQL Server are:
- install the Oracle client drivers on the SQL Server machine;
- install the Oracle client ODAC (Oracle Data Access Components);
- in the linked server providers, configure the OraOLEDB.Oracle provider to allow Inprocess.
Now you can choose:
Finally: you have to configure the security, i.e. the login used to access the Oracle server.
About the two final steps: you can use the SQL Server Management Studio (as described in the first link) or via stored procedures (as in the second link).