iTerm2 does not show username, machine name, time On my new mac machine, I could not do autocomplete for Git when I hit Tab.

So I thought to modify the terminal and found certain things on this link.

I may have messed when I installed iTerm2, Oh-My-ZSH, and Solarised Dark. So now I have nice looking terminal and git autocompletion works. 

But in the terminal, the user name, machine name etc does not appear, like it is the in above link.

.

The colour scheme is also not great.

Can someone please help me, possibly step-by-step, on how to show these things like in this image 

I am very new to Mac and please assume that I know very little about how it works.
Everything you're asking has more to do with the shell than with iTerm. There are numerous tutorials on how to set up your PROMPT variable (I use a modified version of this one). Since you're using Oh-my-zsh, try looking through the themes page. There are a variety of styles available (I began with the af-magic prompt). Once you find a prompt you like, feel free to copy the source from the .oh-my-zsh/themes folder to .oh-my-zsh/custom/themes and modify the custom version. Details on custom plugins and themes are available here.