Extracting grouped layers from psd

I am a developer and working on an application whose designs I have received as a PSD file. But I am totally a beginner in designing. I have installed Photoshop in my computer but have no idea about how to save a layer out of that.

There are buttons in the PSD which I want and I have hidden all other layers except the one I need. Now I want to save it but I am just not able to do it. I have searched on google but could not find any solution.

1. Select the layer you want to export
2. Select All (control/command + shift + a) then copy merged (control/command + shift + c)
3. Create a new file (control/command + n) (Edit:)Make sure Preset is set to Clipboard, then hit return. It will automatically be the right size of the clipboard
4. Paste (control/command +v) then Save for Web... (control/command + alt + shift +s) and then follow the dialog.