Extension of custom UI5 application

Dear UI5 Experts,

  I am in a support project and now I have to extend the SAPUI5 existing application which is custom build.

  I have a simple task.

  I have to extend the application by adding a input text box.

  I know how to do that from the coding prospective.

  However I don't know the procedure to extend it in terms of application itself.

  I am using Eclipse for development.

  I know that I can download the existing UI5 application which exist as BSP application in sap to my Eclipse but I do not know

  if I change it and upload it again would it disturb the existing setting.

  Kindly provide me some guidelines.

Thank you