Update README.md

Author: RijulGulati

README.md

@@ -1,2 +1,42 @@
 # go-andotp
-CLI program to encrypt/decrypt andOTP files
+CLI program to encrypt/decrypt [andOTP](https://github.com/andOTP/andOTP) files.
+
+## Installation
+```
+$ go get github.com/grijul/go-andotp
+```
+
+## Usage
+```
+Usage: go-andotp -i <INPUT_FILE> {-e|-d} [-o <OUT_FILE>] [-p PASSWORD]
+
+  -d    Decrypt file
+  -e    Encrypt file.
+  -i string
+        Input File
+  -o string
+        Output File. If no file is provided, output is printed to STDOUT
+  -p string
+        Encryption Password. This option can be skipped to get password prompt.
+```
+
+## Examples
+- Encrypt JSON file (Password is asked after hitting ```Enter```. Password is not echoed)
+```
+$ go-andotp -e -i file.json -o file.json.aes
+```
+- Encrypt JSON file (Password is entered through CLI)
+```
+$ go-andotp -e -i file.json -o file.json.aes -p testpass
+```
+- Decrypt JSON file
+```
+$ go-andotp -d -i file.aes.json -o file.json
+```
+- Decrypt JSON file and print json to console
+```
+$ go-andotp -d -i file.aes.json
+```
+
+# License
+[MIT](https://github.com/grijul/go-andotp/blob/main/LICENSE)