Since you already had CM10 installed, you should be having the ZIP file with you.
If you do not have it, you can download it from the previous source and place it in your sd card. If you do not have and do not know the source from where you already downloaded, you can try the one from where I had downloaded (Courtesy).
The reason I am trying to stick to your previous download is that these ZIP files are unofficial CM builds and are compiled from same source by many developers, each adding their own bells and whistles and most importantly bug fixes. Hence you already know what is working and what is not with your previous ROM which will avoid you any nasty last minute surprises.
As far as the ROM that I am using, apart from what is mentioned in the blog, Google location service is not working. Which means that News and Weather app, Google maps etc will not get your location without GPS.
After deciding which ROM ZIP file to use, place the ZIP file in sd card and switch off the phone. Please backup whatever you want as the following steps is going to erase all except the SD card contents.
- Reboot your phone into recovery mode. To do this, press and hold Home button, Volume down button and while holding both down, power on the device. Do not release the home and volume down button until you see the CyanogenMod recovery console.
- Then simply follow the steps as said in the blog.