Step 1: Download
Frist downlaod all three parts of the mod.
Step 2: Install
Next place all the files you just downloaded in the fallout new vegas data folder and merge the folders if asked.
Step 3: Download FOMM(optinal but recommended)
Now if you want, and I recommend it. Download Fallout mod manager from the website newvegasnexus.com and install it. If you do download FOMM open it after you installed it and place a cheack mark next to SunValley.esp and click Launch Fallout new vegas then have fun and play.
Step 4: Start Sun Valley
If you didn't download FOMM, then launch fallout new vegas like normal. when the launcher apears, click data files and place a check mark next to SunValley.esp and then click play, then just have fun and enjoy!