If you know that you are looking for a job with a specific company, simply put "company:" in front of the company name in the keyword area. While putting in a company name without company: in the keywords area will often lead to the correct results, you may actually get listings not related to actual company if you are using a company that has a common identifier ("General Motors" for example, might pull listings from General Motors & General Electric because the word "general" is in the listing).

Example using Pfizer

You can also surround the company name with () to make the search even more exact. Example using General Motors