diff --git a/README.md b/README.md
index 9f4b5cc..320171c 100644
--- a/README.md
+++ b/README.md
@@ -1,3 +1,34 @@
 # kwh-calc
 
-Calculate cost of electricity.
\ No newline at end of file
+Calculate cost of electricity.
+
+## How to use
+
+```shell
+$ kwh-calc [OPTIONS] price wattage interval [interval ..]
+```
+
+Options are -v, --version to show program's version; and -h, --help to show usage of a program.
+
+`price` is a price per KWh. `wattage` is how many Watts being consumed. `interval` is for how long.
+
+`interval` is in seconds, but you can specify a unit. Units are the following:
+`m` for minutes; `h` for hours; and `d` for days. There could be as many `interval`s passed as you need.
+
+Here is an example:
+
+```shell
+$ kwh-calc 3.68 120 30d 2h
+```
+
+P.S.: Yeah, I pay 3.68 rubles per KWh. Which is just $0.05. :)
+
+## Installation
+
+### Manually
+
+First run `make` to build a program, and then `make install` to copy executable in `/usr/bin/`. Later, use `make uninstall` to delete it, or just delete `/usr/bin/kwh-calc`.
+
+### For ArchLinux
+
+You can take a [PKGBUILD](/raw/branch/master/PKGBUILD) file and in a directory with it run `pkgbuild -i`.
\ No newline at end of file