Done what is suggested in both of these replies. No joy.
Yes a box comes up a blue bar fills up from left to right. It tells me the printer is not connected. It seems to know about my printers which I never told it. Some places in the attached jungle I keep seeing 'deskJet 2540 series' or c'. So these must be the two printers. They now appear at the bar the bottom of the screen, forget what what is it's called. They tell me 'printer not connected'.
So how do I connect the printer? In a simple way as everything seems to be ready.
I have been here. Recommended settings for Wi-Fi routers and access points - Apple Support
Looks stultifying. Already been to places like that. Completing seems to involve answering a lot of questions I don't know the answer to.
Tried this https://www.youtube.com/watch?v=PMo7zifSjxo
You have to go to a place called hardware in Settings. There is not a place called hardware in my settings, but at least I found printers there. Again it knows about my printers. One of them and it tells me is 'in use'. I turn it off (the other one is turned off) and it still tells me it's in use. And also that it is not connected which is what I went there for.
And I have also been round the houses with the General Mac instructions for how to connect printers.
One of the things I never understand is you have to connect to a wi-Fi network. But which network? If I look for the networks I could connect to there is my BT which is my Internet connection etc, and my printer is another network. Anyway neither is ever worked for this.
By the way one of the stultifying things I came across in the Mac instructions was about insert at some point a TTIP/IP Number or identification. I asked in the Apple shop what that was how do I find it out and they told me it's on the printer. Ah the printer! I would never have guessed.
Also because when I look on the printer I find no number likely to be that.
It can't be this difficul surely!?