You will need
Create a new document by going to the settings command New from the File menu. Select the RGB color mode from the Color Mode list. In the list of Background Contents select White or Background Color. Make the main color any color different from the background. It will need to draw a circle was visible.
The most obvious way to draw a circle is to obtain the impression of a round brush. Select the Brush tool, go to the Brushes palette and click Brush Tip Shape. If you can't find the palette of brushes in the graphics editor window, expand the option Brushes from the Window menu.
Select one of the round brushes and remove the ticks from the checkboxes to the left of the names of the tabs palette. Tab Brush Tip Shape, adjust the size of the brush, putting the desired size in pixels, drag the slider Diameter. If you need a circle with sharp edges, set the Hardness to its maximum value. The smaller this parameter value, the more feathered the edge will have the imprint of the brush.
Put the pointer to the new document and click the left mouse button. The circle whose diameter equal to the diameter of the brush-configured, ready.
Another way to draw a circle is to create a round selection and fill color. To do this, select the Elliptical Marquee Tool in the tools palette, place the pointer to the open document and start to draw an elliptical selection. In the process of creating the selection, press the Shift key and hold until you get the desired range of diameters.
Fill the circular selection with any color or texture using the Paint Bucket Tool. In order to use the texture to fill the circle, select Pattern from the list in the tool options bar Paint Bucket.
Another way of drawing a circle in Photoshop is to use the tool the Ellipse Tool. Select this tool from the tool palette and put it in the mode to Fill pixels, by clicking on the button in the settings panel that appears under the main menu after you activate the Ellipse Tool.
Begin drawing the ellipse and press the Shift button. The created figure will transform from ellipse to a circle filled with the foreground color.