I have about 300 digital photos on my digital camera mainly on flowers and other topics.I would like to earn some money on them.Can you guide and help me in this regard?

First, in order to make money selling photos they have to be:

1) Exceptionally good - correct focus, color, composition, etc.
2) Processed in Photoshop - no photo "straight out of the camera" is ever ready for sale.
3) Better than the millions of similar photos already offered for sale.
4) Keyworded with all the words someone might use to try to find a photo like this one.
5) Something new - a new subject, a new composition, a new way of lighting the subject, a new photo technique.

When you have photos that meet this criteria, then you can look at listing them with stock or microstock agencies. Stock agencies get the highest rates for the photos, but it's very, very hard to break into the stock agencies when you are an unknown photographer. The work has to be the very top quality and most experienced photographers never break in. Microstock agencies pay very, very little per image, often just a few cents. The effort to list your images with a Microstock agency may not pay off unless you have many thousands of images.