Unable to update repo

[PercyP]

Hi,

I hope I am in the right place?
I made the mistake of following some instructions online to install FFMPEG. I basically had to install some repo.? which I have now discovered is so out of date. Is there a way to uninstall this and then install the correct up-to-date version?
When I run yum update I get the following error:

yum update
Loaded plugins: fastestmirror, security, universal-hooks
Setting up Update Process
Loading mirror speeds from cached hostfile

• EA4: 85.13.201.2
• cpanel-addons-production-feed: 85.13.201.2
• atomic: www4.atomicorp.com
• base: mirror.sov.uk.goscomb.net
• extras: mirrors.coreix.net
• updates: mirrors.clouvider.net
  http://apt.sw.be/redhat/el6/en/x86_64/dag/repodata/repomd.xml: [Errno 14] PYCURL ERROR 6 - "Couldn't resolve host 'apt.sw.be'"
  Trying other mirror.
  Error: Cannot retrieve repository metadata (repomd.xml) for repository: dag. Please verify its path and try again

Would you know how I get rid of this so I can install the correct version?

Kind regards

PercyP