The quick search looks at Contact Firstname & Lastname, Company name and Contact and Company ID.
Start typing the first name or last name of a contact or company name and the quick search will display a list of contacts and companies based on those characters. The more characters you enter, the narrower the list of possible results.
Click the appropriate contact/company from the filtered list, then click 'Load'. (Or use the arrow keys to navigate to the record and press ENTER twice to load the record).
If you fully type in the contact/company, but do not select it from the predictive list, the CRM will fail to find a matching record.
If you know the contact or company ID, you can also search by typing this number into the search field.