How to zoom in Xcode on a code window

I needed to install a plugin to have the functionality - This is the plugin https://github.com/zats/AdjustFontSize-Xcode-Plugin

I'm using xcode 7:
1. Xcode menu-> Preferences.
2. Choose the tab Fonts & Colors.
3. Choose theme on the left side.
4. On the right side cmd+A to choose all type of source.
5. In font field, click to T icon.
6. Choose a font size that you want to set.

For XCode 9 and above: