To search across the whole collection, use the Search box on the main page.
Once you have a search, you can use the Advanced Search option to narrow by date. The links will point to the text for the article as captured by OCR and to the article in the actual newspaper. Usually, the newspaper is much easier to read than the OCR output.
The advantage of the search at the University of Illinois Digital Newspaper Collection is that it has articles in its structure and it highlights the search term in the actual document.