The easiest way:
1. Get a image that is bigger than 800x100 and use it as a banner (resize and/or crop if needed)
অথবা make it online.
The hardest way:
1. Get photoshop অথবা something like that
2. Start a new project
3. Enter the measures (800x100)
The পরবর্তি steps will only depend on how good আপনি are with it 4. Select a few প্রতিমূর্তি আপনি want to use and open them (it won't affect your project)
5. Chose the part of the pictures আপনি want to use (If আপনি wanna use the entire picture, just copy and paste it there)
6. Add a few effect অথবা text
7. Save it as a image file (.jpg, অথবা .png)
the hard way is way আরো complex than that and requires a bit of skills around an image edition program (which requires a lot of practice and time), so if আপনি want something quick, go for the easy way.
Plus, check
link for আরো help.
