Can’t Link to External Website

Hello. I can’t seem to link to external pages using texts, icons, or images.

I wanted to link to my Twitter and LinkedIn profiles using the social icons. But every time I put the link (for instance, http://www.twitter.com/username), I’m always directed to https://www.domain.com/www.twitter.com/username.

How do I change it to just http://www.twitter.com/username or http://www.linkedin.com/in/username?

I’d really appreciate a response. Thanks in advance.