Go to the play store on your phones browser, and search for google wallet, (sign in with your gmail account at any time). Complete all actions using your browser(or any PC). Your nexus should show up as a compatible device, and should be able to install...IF it doesn't...
Go to the play store in your phones browser(sign out of your gmail account up if it shows you as signed in). Search for google wallet, (choose to complete the action with your browser until i specifically mention not to). Click on the picture for google wallet, not the install button. When the next page loads, click on the install button, it should then pop up a dialog box with the option to sign in. Click sign in, and sign in with your account, after you are signed in with your browser, use the back button twice, you should then get the dialog asking how to complete the action (browser or play store) choose play store and your play store will open up to the wallet page, where you will be able to download and install.