Log in to your wp-admin site as you would normally. When you click on Media on the left hand side of your Dashboard you have two options; you can view the images in the existing library or uploading images to WordPress.
If you click on Library you’ll see all the images currently uploaded.
If you need to upload an image to use on a Page or Post you need to prepare it for upload first.
WordPress will generally re-size your image automatically to the place you want to use it. However, there’s no point loading images that are over 1000 pixels wide or tall because they’ll not fit on the majority of screens when viewed actual size. Stick to 100 – 600 pixels wide or tall as a maximum, reducing large images to this size will reduce the file size too.
It is important that you don’t upload images that are too large as this will slow down your website. I’ve attempted to illustrate this with the image above! You need to ensure images are no larger than 500KB – ideally they’ll be around 100-150KB. You can re-size images using any number of software packages like Adobe Photoshop, Microsoft Office Picture Manager or Paint.
Once you’re satisfied with the size of the image, you need to give it a name. It’s recommended that you use lower case text to name your image and that you separate any words using hyphens. You need to do this before you upload the image. I wrote another article about how to upload optimised images that you might find useful.
After clicking Add New you’ll be taken to a page where you can drop the image you want to upload, alternatively you use the click here button to browse for the image on your computer.
Once the image is uploaded you’ll see a thumbnail of it – click on the blue Edit link next to it.
Here you’ll see a preview of the image at full size. You should then remove the hyphens from the Title field (top of the page) and replace any lower case letters with upper case letters as appropriate. When you’re happy with the Title, copy and paste it into the Alternative Text field further down the page. You can ignore the Caption and Description fields.
Click on the Update button on the right hand side when you’re finished.