Hello Salaom Pradeep,
Please find answer to your question.
How release parameter are integrated to deployment plan?
Release parameter are used in a process and these process are mapped to either deployment steps, Initialization etc. Once the template or deployment plan is created using the process which are using the Release Parameter it will show on the ROC UI. For example screen shot below. Release parameter expect the value to be there before the process using them is executed.

How release parameter are used in manifest file?
Once you have created the template or deployment plan you will see below options which is out of the box feature of the product to generate automatic manifest file based on your template or deployment plan design.
Template-> Generate Manifest Deployment Plan->Manifest->Download a manifest template

Once you downloaded the manifest file from respective stage you need to fill the values in place holder. For example in above example expected values are two release parameters.
Sample manifest file generated automatic

The value filled above is Rparam1 and Rparam2
Now you can load this manifest file into the deployment and the parameter values from this file will be filled in respective release parameters.
Regards,
Saurabh