In the Language section at the top of the "General" tab, click Show all language options and check the box for Enable input tools.
In the “Input Tools" window that appears, double-click the input tool you'd like from the "All input tools" field, and it'll move to the "Selected input tools" field.
You can reorder your input tools by selecting one of your input tools and clicking the up and down arrows.
The keyboard icon indicates that you’ve selected a virtual keyboard.
Click Save Changes at the bottom of the page.
OPEN GMAIL SETTINGS
You can edit these selections at any time by returning to your settings and clicking Edit tools in the “Language” section.
How to use Input Tools
Once you’ve enabled an Input Tool, you can turn it on and off using the button next to the gear icon in the upper right corner of Gmail.
If you've enabled multiple Input Tools, you can click the down-arrow menu to switch between them.
Types of Input Tools
Handwriting input: Write words directly with your mouse or trackpad.
Transliteration: Type languages phonetically in English letters, and they'll appear in their correct alphabet. Keep in mind that transliteration is different from translation; the sound of the words is converted from one alphabet to the other, not the meaning.
Input Method Editor (IME): Use a Latin alphabet keyboard to convert your keystrokes to Asian characters. We offer a handful of IMEs like Pinyin and Wubi IMEs for Simplified Chinese, as well as Pinyin and Zhuyin/Bopomofo IMEs for Traditional Chinese and Japanese.
Virtual Keyboard: Use an on-screen keyboard native to languages like Arabic, Hebrew, Thai and Korean.