How to take the Mew in this game?

"Pokemon Yellow Cheats, Codes and Tips:
-The Mew glitch

First off, this glitch should be done by the beginning of the game. To get the Mew glitch, here's what you need to do. First, you need to have somebody with Teleport or fly. Teleport is way more practical at the beginning though. So what you do is first, you have to go right above the guy to the left of the Nugget Bridge. Then, walk down one spot, so he would come up to you. But, you need to pause the game before he comes toward you. This might take a while, so make sure you save it.

Now that you are at the menu, you need to teleport back to the city. The menu will not work now, so you know it's working. Next, go back over the bridge. Now, you have to get to a certain trainer that's to the northeast of Nugget Bridge.

To beat Brock easily, get either a Nidoran (male or female will be sufficient)or a Mankey and train them until they learn Double Kick or Low kick respectively. "

It was in the Cheat and Codes section.

You can always just watch the video on how the glitch works also. Here is a link.