Update README.md

README.md

@@ -1 +1,11 @@
 ## Simple count down timer application for flipper zero
+
+### How to use
+`up/down`: set second/minute/hour value.
+
+`ok`: start/stop counting.
+
+`long press on ok`: stop counting and reset counter.
+
+`left/right`: select second/minute/hour value.
+