Since there are a number of stock agencies on the market, you have to find the right one first. To increase my revenue, I am currently working with five different equity agencies (Shutterstock, Adobe Stock, iStock, Dreamstime and Colourbox). I also tried other agencies, but either the sales there were too low (123rf, Zoonar) or the uploading of the pictures caused problems (Alamy, Bigstock).
An overview of the stock agencies with which I work and have had good experiences (Alamy is still there, but I don’t upload any more pictures there) can be found here. The page opens in a new window and if you click on the pictures of the individual agencies here, you will come to my respective portfolio of the agency. Here you can also find the instructions and guidelines of the agencies to become sellers yourself.
It is also possible to sell pictures exclusively to a stock agency, which leads to higher yields. However, you may not offer the pictures at other stock agencies. I don’t use it and prefer to operate multiple agencies at the same time to increase my earnings.