desktop internet connection

I had internet, thru a DSL, on my desktop. I tried to install a LINKSYS router to get my laptop onto WI-FI. Well, it did not install apparently, and I could not get the WI-FI to work.
So I tried to connect my desktop BACK to the cable thru DSL, and now I don’t have an internet connection to my desktop.
It says not connected.
How do I find out what to do to get my desktop reconnected to the DSL??

also, the DSL modem does work, as I can connect my laptop to the same cable and it will connect to the internet. So the modem is working OK, however I don’t know what to try?

Can anyone give me some direction?

thanks,
George