WordPress has a defined format for galleries. You can include your own gallery just uploading the pictures to the same post/page where you want them to appear.
When you upload your images to a post like this one, you’ll get a new tab on the upload/insert feature on the edit page.
In this ‘gallery’ tab you can quickly insert a gallery clicking on the ‘Insert Gallery’ button:
This is a example of a WordPress Gallery with 3 images plus the screenshots included in this post:
The reason why the screenshots are included is because we uploaded inside the post editor for this post. You obviusly wouldn’t want this to happen with your pictures, so be sure to go to your media library and upload the file from there. Don’t upload the file from the post, because then it will keep attached to the post and be displayed in the gallery.
If necessary, delete the image you uploaded from the post editor and upload it from the media. Wordpress still doesn’t have a full media functionality for attaching or re-attaching images to posts.
After you do this, you’ll get something like this:
In spite of lack of functionality, it’s still very useful to have your post/page galleries well done. In the future, when you start programming and changing the theme’s code, you’ll find useful to have all the images well attached so you can call them from your PHP code easily.