Computers can be good quality and bad quality depending if its used  or new. Used can be good if the formal owner didn't damage it. However, i  never take such a risk and i always recommend getting new.
Now  that you have your computer, you are going to open it from the box  really carefully. This is not a toy. And when its opened , you are going  to have to look for the ON button which is usually on the front of a  case or a laptop, and its location  will be given in the manual so don't  worry.
Then you are going to have to type some  information the first time you turn it on. You are going to have to  install some drivers and they will give you the option to select WiFi  wireless(If password is known off course). And you will be able to type  the username and password for this specific account. And when all the  typing of the information is done, you will have to install the most  important things:
THE MUST: Anti-Virus: Now, if you  don't know much about the Anti-Virus, it is a software that you install  that will keep your computer safe from a lot of viruses that come from  the web or from other sources like your friend's Flash Memory that may  be put in your computer and that might have a virus in it. SO BE  CAREFUL!
THE MUST IF NECESSARY: Microsoft Office: If  you are a business man , that arranges  business files and papers , you  are going to have to need Microsoft Office. Its very important and its  one the top Programs for Writing Script and making Presentations.
Photoshop:  If you are a Graphic Designer, you are going to have to use this  program to design logos and signs and many other stuff. Photoshop is  great for masking Photoshops and overlapping images and organizing  layers.There are a lot of tutorials on youtube for Photoshop if you are  interested in Designing. 
Thank you for reading this post, and remember to contact me a Karims27@hotmail.com for more information