put a plug in for (someone or something)
To speak very highly of or enthusiastically endorse someone or something, as a means of marketing, advertising, or professionally recommending them or it. I was really impressed with your work, so I'd be more than happy to put a plug in for you the next time someone asks me for a mechanic. We're willing to pay you a generous fee if you put a plug in for our new product on your radio show tonight.
put a plug in (for someone or something)
to say something favoring someone or something; to advertise someone or something. I hope that when you are in talking to the manager, you put a plug in for me. I could use some help. While you're there, put in a plug.