photoshop is the industry standard image editing software. you can use MS PAINT on your system to make graphics. Or download paintshop pro, or other freeware/shareware) or you can go to a website where u can make/edit graphics with no software. search for "free online photo editing"
One of the most popular free graphic programs is GIMP/GIMPShop. You can also try InkScape if you want a vector program.
Photoshop is the best tool in industry, Otherwise there are many software present in industry now those you could use for create graphics... Some of them are vector based so you have to export your graphics in image from. Softwares are... Photoshop Corel Draw Illustrator Image Ready Corel Photopaint etc.