[Theme: Lambda] How to create custom button

So, first of all I have to say I’m the noobiest noob you can ever find, so I only know the basics and I’m working with Visual Composer because I don’t know how to use CSS yet.
The problem I have is that I don’t know how to create a custom button. I wish to create my own log-in button that would lead to second site that is not connected to this one (word press site). I’ve tried lots of plugins but non of them works (or I don’t know how to work on them LOL) how I want them to.
Anyone has any idea what plugin to use or something else?
Thank you.