Add readme instructions

README.md

@@ -1,2 +1,34 @@
 # subfield
-A sub-field accessor macro for the Nim programming language.
+A sub-field accessor macro for the Nim programming language. This lets you access nested fields within a Nim object or ref object.
+
+# Installation
+
+```bash
+nimble install subfield
+```
+
+#Usage
+
+```nim
+import subfield
+
+type
+  C = object
+    y: int
+  B = object
+    x: int
+    c: C
+  A = ref object
+    b: B
+
+var c = C(y: 0)
+var b = B(x: 5, c: c)
+var a = A(b: b)
+
+echo a.x
+echo a.y
+
+# Prints:
+#  5
+#  0
+```