Update README with instructions.

README.md

@@ -1,2 +1,41 @@
 # ccclip
 End to end encrypted cloud clipboard.
+
+# Installation
+
+Download the prebuilt latest release binary for your OS/arch and ensure that it's in your path.
+
+# Configuration
+
+By default, ccclip looks for a ccclip directory in the [user home directory](https://pkg.go.dev/os#UserHomeDir) and it'll store the configuration file and device keys there.
+You don't need to do anything if you want to stores your config in the default location; to override this behavior, use the `--config-dir` global flag.
+
+# Instructions
+
+### Create an account with
+
+```bash
+ccclip register -e {your-email}
+```
+This will prompt you for your password. Your input won't be shown, that's expected (we like to be safe right!?). Just press enter.
+Passwords are stored as bcrypt hashes in the server.
+
+### Register your device
+
+```bash
+ccclip register.
+```
+This will prompt you for your password.
+An [X25519](https://pkg.go.dev/crypto/ecdh) key pair is created and stored in your configuration directory.
+A "device" is created and associated to your account, the device id is stored in your configuration file.
+Only the public key is sent to the server (duh).
+
+### Save and retrieve your clipboard
+
+The root command `ccclip` serves both purposes, if you pipe something to its stdin, it'll read it and save it as your clipboard.
+If you don't pass anything then it'll retrieve your current clipboard and output it through stdout.
+
+There's a caveat: When a clipboard is created, the sending device encrypts the data for each of the currently registered devices
+individually. This means that if you register a new device, it won't immediately have access to the current clipboard because
+its public key wasn't available when the clipboard was created. The benefit of this is that your data is end-to-end encrypted and I'll never
+be able to see it nor an attacker if we're compromised :)