Hi,

If you are looking how to import data in odoo, you can use the default import option in odoo, to know about how it works, have a look at this official documentation about the same.

See: How to Import data

Integrating with External Applications

Odoo is usually extended internally via modules, but many of its features and all of its data are also available from the outside for external analysis or integration with various tools. Part of the Models API is easily available over XML-RPC and accessible from a variety of languages.

See this:  External API

To understand different use case of odoo xmlrpc and jsonrpc, see this tutorials: Odoo XMLRPC : Connect Odoo With External Applications

Also see the answer for this question:  How can I integrate other business systems or technology solutions with Odoo?

And if you are new to odoo, for reference you can use this links:

1. Odoo Elearning

2. Odoo Documentation

3. Developer Documentation

4. Odoo 14 Development Tutorials

Update:

For Calling Existing Menu Action in Custom Module

1. Open the menu/action that you need to call in custom module.

2. Activate the developer mode

3. Click on Debugger Button at the top right of the screen near logged in user name, click Edit Action

Copy the External ID.

5. Add new menu in custom module and add new menu and set this external id in the action of the menu.

<menuitem id="test_menu"
          name="Menu"
          action="hr.open_view_employee_list_my"
          sequence="10"/>

As the action exist inside the hr module, make sure that hr is given as depends in the manifest file.

Thanks