https://steemconnect.com/sign/account-witness-vote?witness=swisswitness&approve=1
this is the link to vote for my witness for example : @swisswitness
if you change the name in the link to curie then you get
https://steemconnect.com/sign/account-witness-vote?witness=curie&approve=1
and so on, you can check witnesses here, this is the fullest list i know of
https://steemian.info/witnesses