There are two main ways to use proxies in Scrapy. You can either use it per request basis or use it with every scrapy outgoing request.
How to use proxy with a single request
proxy = 'proxy_here'
return Request(url=url, callback=self.parse, meta={"proxy": proxy})
How to use proxy with every request
Go to to middlewares.py
and update process_request
method and paste following code
proxy = 'proxy_here'
request.meta['proxy'] = proxy