What are primary sources?

created by a person or people who directly experienced or witnessed an event
document evidence of that event, which can take many forms: photographs, research data, research reports, diary entries, eyewitness accounts, and more

is created by a researcher in that field, or a group of researchers working together
documents an experiment, study, or intervention conducted by the creator(s)
includes evidence, typically collected data
also cites prior evidence created by other researchers in the field
uses more formal, technical terminology than everyday discussion of the same concepts
is primarily written to be read by other experts in the field
is published in a peer-reviewed journal

Some examples

A randomized controlled trial of resistance exercise training to improve glycemic control in older adults with type 2 diabetes
Randomized controlled trials are a type of primary research in science and medicine. This is an example of the kind of article you are looking for.
The Effect of Exercise on Insulin Action in Diabetes
This is another example of a primary research article. However, it might not be the best choice of source for your paper. Can you tell why?
The essential role of exercise in the management of type 2 diabetes
This is an example of a review article, a type of secondary source that summarizes and analyzes primary research articles. This is not a suitable choice for your papers because it is not a primary source. However, it may still be useful to you. Can you tell why?