Hi,
I explain in this post how to import a lot of computer hostname with mac adresse or smsbiosguid for prepare to deploy operating systems (example : Windows XP, Windows 7 or Windows 8 and servers operating systems).
Let's GO !!!
For start, you do create a file (with notepad) with information indicate under, (for SMSBIOSGUID, you can add or replace by mac address informations.)
After indicate the netbios name and the mac address, you can save your files with *.csv extension. (insert add SMSBIOSGUID and Mac address, you indicate this Hostname,SMSBIOSGUID,Mac address.)
Open the SCCM 2012 console and select Assets and compliance TAB, right click on Devices and select
Import Computer Information.
Select Import Computers using a file and click Next
Browse and select the *.CSV file
Select the CSV file (in my example, my file is named import.csv
Attention: Replace the Assign as by the good setting, in my example, i use the mac address...
The information appear and you can click on Next
click on Next
Select the target collection to import the computer information and click Next
Click Next
Click on Close
All computer informations is correctly imported int he target collection (collection properties)
And all computers information is good present in the collection, so EASY, No? 
Finish
You can read all others post on SCCM 2012 under (OS deployment):