Please follow the next steps in order to find the ID:
1) Go to Follow Company or Showcase Plugin Page. If you haven't signed in yet, click on "Sign in with LinkedIn".
2) Enter your Company or Showcase Page Name in the appropriate field and click "Get Code" button.
3) A field will appear with a data-id. The number in quotes is your ID.
4) Copy the ID and paste it in "Company or Showcase Page ID" field.