President John F. Kennedy and First Lady Jacqueline Kennedy Attend Ballet Folklorico Performance, Mexico City, 1962. ST-C1-11-62. Used with permission, John F. Kennedy Presidential Library and Museum.
Whenever possible, search a reputable collection for original, high-quality scans. You are more likely to find accurate information as well as usage guidelines.
A good quality site, such as university, museum or special collection archive, provides basic information such as artist/photographer, date and location.
In addition, you may find helpful notes or description to place the image in historical context. Do not use this information as your secondary source as it will not have gone through the rigor of peer-review, but do use it as a 'launch pad' to understanding your image, its importance, and application to your historical topic.
Google Images is one way to locate historical images but has some challenges as well.
Here is a video on following a 'breadcrumb trail' in a Google Image search to a source you can cite. [adelitas example]