If you mean setting your NaNo goal on the Prep log spreadsheet, that's set when you sign up. We can change it upon request. Looking at the spreadsheet, it seems someone has done so. Your goal there is currently set at 50,000, which is the standard NaNo length.

If you mean on the NaNoWriMo site itself, I haven't been there in a while, but as I recall there's a way to set it there, too.

And if you mean the Writing.com NaNocounter, instructions for that can be found here: "WDC Features for NaNoWriMo Participants" 

Sorry if this is confusing, but it's not exactly clear to me what you're asking for. I hope this helps.