update group example readme

examples/groups/README.md

@@ -9,5 +9,27 @@ leo build
 
 To run this program, run:
 ```bash
-leo run
-```
+leo run main
+```
+
+## Overview 
+
+This example shows how to do basic operations over groups.
+
+It takes the input data from inputs/groups.in
+
+
+## Documentation Group Element
+
+The set of affine points on the elliptic curve passed into the Leo compiler forms a group. Leo supports this set as a primitive data type. Group elements are special since their values can be defined as coordinate pairs ```(x, y)group```. The group type keyword group must be used when specifying a pair of group coordinates since implicit syntax would collide with normal tuple (a, b) values.
+
+```
+let b = 0group; // the zero of the group
+
+let a = 1group; // the group generator
+
+let c = 2group; // 2 * the group generator
+
+let d = (0, 1)group; // coordinate notation
+```
+