Cloud cover percentage in Google Earth Engine

I'm doing a project at my university about the Cloud cover percentage in determinate areas in the world. I'm completely new to Google Earth Engine and I'm struggling a lot trying to find a solution for this task. The main problem is how to obtain the percentage of cloudiness in a certain pixel of a list of images.

Here is just the beginning of the code, hope you could help.

//coordinates Pavia
var city = ee.Geometry.Point(9.15, 45.18);


//add point on the map 
Map.addLayer(city);

//dates of interests
var start = ee.Date('2016-01-01');
var end = ee.Date('2017-01-01');

//image collection
var Pavia = ee.ImageCollection('LANDSAT/LC08/C01/T1_SR')

.filterBounds(città)
.filterDate(start, end)
.sort('CLOUD_COVER', true);