Do you want to develop BPEL ??

1. Go to http://www.oracle.com/technetwork/developer-tools/jdev/overview/index.html

2. Download JDeveloper 

3. Install and configure

4. (Search for "JDeveloper Extensions" using CTRL - F (browser Search) in http://www.oracle.com/technetwork/developer-tools/jdev/overview/index.html Select "Oracle Fusion Middleware")

OR

Go directly to http://www.oracle.com/ocom/groups/public/@otn/documents/webcontent/156082.xml
and download Oracle SOA Composite editor (File name:soa-jdev-extension.zip). Ensure that you are downloading same version as your JDeveloper


5. Select JDeveloper select Help->Check for Updates. Click Next and Select Install from Local File and browse to where you saved soa-jdev-extension.zip. Click Open, click Next and then Finish. JDeveloper will then install the extension; finally restart JDeveloper when prompted