If you search "File Patch code 3.5.1 NTSC" on Google i'm sure you'll find it. To use it, you gotta make a .txt file. (on the Homebrew Browser, there's an app called Accio Hacks. This app is optional, but it does give you a full codelist for SSBB.) Get Accio Hacks and run it from the HBC. it'll have options for what codes you want. just click click on whichever options apply to you. Now, in Wii games, click "S" when the alphabet shows up, and go down to SSBB. click it, download it.
on your SD, in your codes folder there should be another folder now, titled "R" or something like that. get to SSBB.txt. now after you've found the file patch code, copy and paste it into you're txt file, the same way the other codes are set up. (code name, creator name, code under that).
Copy you're txt file into the"txtcodes" folder on the root of your SD. You'll need Code Manager to make it a gct. Just search for "Code Manager" in the utilities section of the HBBrowser. Download that, and run it. click on the SSBB.txt and it'll bring up a code list for Brawl. press "+" on the wiimote to apply codes you want, and then press "1" to create your gct. It should appear in your codes folder as RSBE01.gct 
Now you know what to do for Gecko. Start and play! 
Edit: Oh! and if you find an already made gct of the File Patch, just use that, and put it in your codes folder. (name it RSBE01.gct if not already)