How to Upload Custom Logo

Dear Forum Experts,
I am still learning this whole WordPress CMS business of blogs & themes, so please bear with me.
I think this is a great forum as people are very kind & helpful.
I have installed a Business Directory premium press theme a short while ago & am plugging away at it to get a feel of it.
The image file given with the theme is a .psd file. How do we open it?
How can I upload my own logo on the header or front page of my website?
Also, the logo should be clickable & clicking on it should lead one to the main url.

I also take this opportunity to Wish everyone a very Happy New Year ahead!
Warm Regards-Venu