First, check the slider dimensions. Make sure that all new images are cropped to a consistent and correct height and width. Learn more about slider image sizes here.
Tip: You open an image in Photoshop or another image editing software to check the image size.
Go to Content > Media Manager > Photo Gallery. Find and click on the home page slider gallery.
Click on the Add Images button.
Select files from your computer, and click Upload.
Add links and captions to the images, if necessary.
Tip: The gallery is displayed in alphabetical order (capitalized names first), so edit the File Name to control the display order.
Click Next.
Go to the front-end and double check the images dimensions.