The installation has become quite easy from 12c versions of Oracle SOA.
1) Download SOA Suite 12.2.1 from Oracle website which comes with two zip folders. Unzip them to a same directory which will be having two jar files. Now execute below command in cmd console with administrative privileges.
Provide the directory path and select appropriate options which completes the Installation.
2) Now RCU Installtion. For this you must have Oracle DB (I suggest Oracle 11g XE edition).
Once you have DB on your machine go to folder ‘D:\Middleware12.2.1\Oracle_Home’ and execute rcu.cmd file. During the process give DB details which will then creates required schemas onto DB.
3) Now Domain Configuration. For this go to ‘D:\Middleware12.2.1\Oracle_Home\oracle_common\common\bin’ and execute config.cmd file.During configuration select required options and complete configuration.
You can found detailed steps of installation at below link.