Go to this site - http://textsmili.es
Trust the site, it's a Lenny face generator
Do the dream Lenny you love so much.
Copy the Lenny you created and past on chat.
Enjoy

1 Use bracket (shift and 9 at the same time)
2 Space Bar
3 Type 0361 and press alt+x
4 Type B0 and press alt+x
5 Space bar
6 Type 035 and press alt+x
7 Type 0296 and press alt+x
8 Space Bar
9 Repeat steps 2, 3 and 4 in lowest to higher order and put a bracket (shift+0) at the end
10 Ctrl+c to copy it so you dont have to type it, and Ctrl+ to paste it

If you have some difficult, maybe this video can help you