diff --git a/docs/usage.md b/docs/usage.md
index b8dd9f9..0adba15 100644
--- a/docs/usage.md
+++ b/docs/usage.md
@@ -26,16 +26,51 @@ PrivateKey = oK56DE9Ue9zK76rAc8pBl6opph+1v36lm7cXXsQKrQM=
 PublicKey = GtL7fZc/bLnqZldpVofMCD6hDjrK28SsdLxevJ+qtKU=
 AllowedIPs = 0.0.0.0/0
 Endpoint = demo.wireguard.com:51820
+PresharedKey = /UwcSPg38hW/D9Y3tcS1FOV0K1wuURMbS0sesJEP5ak=
 ```
 
 The above configuration is equal to:
 
 ```bash
 wghttp \
-  --peer-endpoint=demo.wireguard.com:51820 \
-  --peer-key=GtL7fZc/bLnqZldpVofMCD6hDjrK28SsdLxevJ+qtKU= \
-  --private-key=oK56DE9Ue9zK76rAc8pBl6opph+1v36lm7cXXsQKrQM= \
   --client-ip=10.200.100.8 \
   --dns=10.200.100.1 \
+  --private-key=oK56DE9Ue9zK76rAc8pBl6opph+1v36lm7cXXsQKrQM= \
+  --peer-key=GtL7fZc/bLnqZldpVofMCD6hDjrK28SsdLxevJ+qtKU= \
+  --peer-endpoint=demo.wireguard.com:51820 \
+  --preshared-key=/UwcSPg38hW/D9Y3tcS1FOV0K1wuURMbS0sesJEP5ak= \
   --exit-mode=remote
 ```
+
+## Dynamic DNS
+
+When your server IP is not persistent, you can set a domain with
+DDNS for it. `wghttp` will resolve the domain periodically.
+
+- `--resolve-dns=`
+
+  By default, the server domain is resolved by system resolver.
+  This option can be set to use a different DNS server.
+
+- `--resolve-interval=`
+
+  This option controls the interval for resolving server domain.
+
+Set `--resolve-interval=` to `0` to disable this behaviour.
+
+## DNS server format
+
+Both `--dns=` and `--resolve-dns=` options supports following format:
+
+- Plain DNS
+
+  `8.8.8.8`, `udp://8.8.8.8`, `tcp://8.8.8.8`,
+  `8.8.8.8:53`, `udp://8.8.8.8:53`, `tcp://8.8.8.8:53`,
+
+- DNS over TLS
+
+  `tls://8.8.8.8`, `tls://8.8.8.8:853`
+
+- DNS over HTTPS
+
+  `https://8.8.8.8`