If you have no experience in working with programs like GIMP and Photoshop this easy task can be quite an issue , best thing to do is decide what software you wish to use and then read some tutorials on how to create a banner with that software , there are plenty around the internet and after a couple of tries you should get the hang of it
Actually, you can create a banner even in windows paint only but Photoshop works better. You have to know what will be the size of your banner would be and what would be its theme for your design. Conceptualize it first before making a move. Try practicing in a simple layout first then create a better one, practice makes it perfect.
There's a lot of tutorial websites that you can use to learn designing. You just need to focus and practice for you to learn faster.
Actually you can use a GIF Animator software to create a banner. It is simple to use and the effects are predefined even a kid can this to create a banner. For more advanced banner making, you can Photoshop and Flash.
Photoshop is prolly the best software to make banners, you can try to search on youtube or vimeo for some good tutorials to start up with.
Internet can provide you different tutorials on how to make a banner. But,I would say that Photoshop is the best!
I think,you can use Adobe photoshop and Flash to design a banner.Because it's a best software to design a banner