update readme

README.md

@@ -7,3 +7,22 @@ The `greenlablib` module is a python module intends to simplify ROOT based routi
 >>> sys.path.append('path/to/directory/where/module/is/located')
 >>> from greenlablib import plot as pl
 ```
+## Usage
+### Plot functions:
+#### improveStyles()
+```
+>>> pl.improveStyles()   # improve the appearance of the data representation
+```
+
+#### [] readFile(file,ncolumns,delimeter=',')
+```
+>>> fname = 'file/path/name'
+>>> ncols = 6 # number of columns in ASCII file
+>>> D = pl.readFile(fname,ncols) # the delimeter can be also set as the last option
+>>> print(D)  # D[-1] stores the number of rows
+```
+
+#### TH1F drawBinContent(bin_arr,val_arr,name='h',title='histo',nbins=100,bin_first=0,bin_last=100)
+```
+>>> pl.drawBinContent(D[0],D[1])  # SetBinContent reimplementation
+```