1. Check your firewall
    Confirm you are not running multiple security tools unless you know what you are doing or they will conflict and block you

If your DNS works, your Desktop &/or AP/Router firewall is not blocking the wallet... you will get connections and Sync without any fiddling with nodes.

if you like to fiddle with nodes anyway...
a) Visit https://chainz.cryptoid.info/mue/#!network and pick a node IP from the node list
b) add the node to your wallet:
- in your wallet QT debug console key it in with the following format addnode [node ip] add
or
- via cli by keying in the following in your terminal mue-cli addnode [node ip] add

that should do it 99.999% of the times... if not.. check in with us on Slack
Cheers!