If you use the Mitingu default themes, there are two different sizes of the main banner.
The Basic Mitingu theme looks like this
To get the image to fit the screen properly, the optium size is 1400 x 300 pixels.
The Stylish theme looks like this
To get the image to fit the screen properly, the optium size is 1400 x 600 pixels.
If you're not an expert on resizing and don't have access to Photoshop, then fear not, we have a suggestion!
There's an online tool called pixlr that's free and will allow you to easily resize banners for web use all day long. You can find it here https://pixlr.com/editor/
Simple resizing of an image
1. Go to pixlr and create/open your image. It's worth noting at this point, that if your image is significantly smaller than the optimum sizes mentioned above, increasing them in size could mean you end up with a pixelated (blurry) image, so it's best to start with an image in or around the recommended size.
2. Click on the Image option.
3. If you just want to adjust the size of your image, select the Image size option.
4. Key in the size. Bear in mind that it's best to keep the Contrain proportions box ticked or the image may look distorted. This might mean you have to do a bit of cropping after you've resized the image.
5. If you need to crop the image then select the Cropping tool.
6. Once you're done select File/Save and then choose either jpg or png from the drop down options.