diff --git a/README.md b/README.md
index b2b89e6..4e1464c 100644
--- a/README.md
+++ b/README.md
@@ -1,2 +1,9 @@
-# sd-card-speed-test
-Bash script for Mac OS X and Linux to test SD card or SSD/HDD read and write speed.
+# Test read/write speed of SD/microSD/USB/SSD/HDD.
+Bash script for Mac OS X and Linux to test SD/microSD card or SSD/HDD/USB drive read and write speed.
+
+Usage:
+```
+$ bash sd_card_speed_test.sh <path to directory which should be tested>
+```
+
+Note: administrator password is necessary for sudo to reset file system cache. Read speed result is incorrect without cache reset.