The link you posted is of Disk Management. If that is where you are trying to set up RAID, that's the problem. Disk Management does not do RAID Management.
In most systems today that offer "built-in RAID" (that is, RAID without using an add-on card), it is done by the mobo BIOS. In the ones I've used, there are two places that need attention. The first is in the BIOS Setup screens themselves. Assuming you're using SATA drives, you need to find the SATA Port Mode setting spot (near where those ports are enabled) and set to RAID mode. Save and Exit. THEN when you reboot you will see a prompt on the screen during the POST process to press a particular key to enter the RAID Setup portion of BIOS. Look in your mobo manual for what this key is. When you hit that, the POST process will stop and take you into RAID Management. That is where you assign particular HDD units to a RAID array. (By default, any HDD not specifically assigned to a RAID array is NOT a RAID drive.) Then you must configure the array you are creating, and ultimately this will Partition and Format those HDD's to create the array. When that is finished, you exit out of RAID Setup and finish your normal boot. THEN you must install the RAID driver for your mobo in Windows, then reboot, so it can start to use this new "drive".
Your system will differ from some of what I have said, I have no doubt. The starting point is your mobo's manual. BUT you also should look for a second manual - it may be a file on a CD that came with the mobo, or you might have to download it - that is specifically all the details of managing RAID systems on your computer. Read it thoroughly - especially in the parts about RAID1, since that's what you are doing - before plunging ahead with RAID setup.
Some systems will allow you to add a HDD to an existing single HDD and migrate the data into the RAID1 array. Some don't. I don't know if that is what you need.
I made a big assumption above. I assumed you want to use the RAID abilities of your mobo and BIOS. I know that Windows itself also has its own system for RAID, but few people use it, and I don't know where you start with that. If that is what you need, try the Microsoft website for info.
There are many problems with doing a hardware raid like that. Namely you have to keep the same mobo, and hdds in order to continue using it. For that reason I wanted to do a software raid 1. It seems there are really no downside to doing it this way. I looked up how to do it and its done in disk management and there's supposed to be a add mirror button but there's not. I can't figure out why...
Unfortunately, Windows 7 Home Premium does not support "Mirrored Array". Only Windows 7 Professional, Enterprise, or Ultimate supports Mirrored Array because Home Premium does not support dynamic disk.