chore: add build instruction

README.md

@@ -1,3 +1,26 @@
-# ksau-oned-api
+# ksau-go
 
 [![Go Version](https://img.shields.io/badge/go-1.23.4-blue)](https://golang.org/doc/go1.23)
+
+## Build Instruction
+### To build this project, you need two important thing:
+1. Private PGP key used to decrypt rclone.conf
+2. The passphrase of the PGP key
+
+### They should be placed under **crypto/** like so:
+```
+└───crypto
+        algo.go
+        placeholder.go
+        >> passphrase.txt  ⌉  -- These files
+        >> privkey.pem     ⌋     they are not provided by the repo
+```
+
+### Finally, install the dependencies and you're ready to build the project!
+```
+go mod tidy  # install dependencies
+make build   # build the project
+```
+
+Depending on the OS you're on, you'll see `ksau-go` or `ksau-go.exe` generated
+in the current working directory.