Start off with opening Photoshop. Once you have Photoshop open go to File>New. Choose the photo option from the drop down menu. Click on the paint bucket and change the colour to black. Now click on the background and make it black. Finally create a new layer. Now you are ready to start creating fireworks.
Step 2: Creating the Firework space
Let's start by creating a grid. Click on the ruler boarder at the top and drag it down to the middle. (You can make the ruler boarder show up by clicking control+r). Do the same on the side ruler boarder. Make sure the lines intercept in the middle. Click the elliptical marquee tool. If you go to where the lines intercept the cursor will turn to a red cross. Now while holding ALT+SHIFT drag the cursor out to make the desired size of circle(firework) you'd like.
Click onto the paint brush tool. Once you have that selected go up to change the brush style. Pick brush #100 and raise up the size of it. Change the brush color to white and then click around the circle to paint around it. Press CTRL+J a few times to create extra layers to make it brighter. Select the multiple layers and right click and choose merge layers. Now double click on the layer to bring up the Layer Style window. Click on Outer Glow and change the colour. Then click Colour Overlay and change that colour as well. Apply effects. Now click on Filter on the top toolbar and choose Blur and then Radial Blur. Raise the amount to a high amount and change the blur method to zoom. Pick your quality based on the speed of your computer. Press CTRL+J a few times to create extra layers to make it brighter. Select the multiple layers and right click and choose merge layers. Here you have your firework.
Step 4: Saving
Go to file, save as and name your PSD file. Then click save as again and save it as a JPEG file. Clicking on the format drop list and choosing jpeg. Now you have your firework to share everywhere. Playing around with different brush types can make different looking fireworks.