update readme

README.md

@@ -4,3 +4,37 @@ Pure Golang xls library
 This is a xls library writen in pure Golang. Almostly it is translated from the libxls library in c.
 
 It has just the reading function without the format.
+
+# Basic Usage
+
+* Use **Open** function for open file
+* Use **OpenReader** function for open xls from a reader
+
+These methods will open a workbook object for reading, like
+
+	func (w *WorkBook) ReadAllCells() (res [][]string) {
+		for _, sheet := range w.Sheets {
+			w.PrepareSheet(sheet)
+			if sheet.MaxRow != 0 {
+				temp := make([][]string, sheet.MaxRow+1)
+				for k, row := range sheet.Rows {
+					data := make([]string, 0)
+					if len(row.Cols) > 0 {
+						for _, col := range row.Cols {
+							if uint16(len(data)) <= col.LastCol() {
+								data = append(data, make([]string, col.LastCol()-uint16(len(data))+1)...)
+							}
+							str := col.String(w)
+							for i := uint16(0); i < col.LastCol()-col.FirstCol()+1; i++ {
+								data[col.FirstCol()+i] = str[i]
+							}
+						}
+						temp[k] = data
+					}
+				}
+				res = append(res, temp...)
+			}
+		}
+		return
+	}
+