First steps - Editing, re-sizing and uploading:
You need to choose a picture you would like to use, you can edit the picture, add text or create a collage through a website like picmonkey (checkout their new effects recently they added stars) once you've edited it resize your image to 250 x 250 this is the normal size button/image you can do this on picmonkey you can make it bigger but I wouldn't recommend any bigger than 350 x 350, once you've done this save your image.
Next upload your image through any website that allows you to do so I use photobucket you need to do this to get your image's direct link.
Second steps - Create HTML code with and without grab box:
Next you want to create a HTML code which is how your blog recognises what you want it to do.
If you want to create a blog button without a grab box/or even image which links to a certain post (like the one I have in my right sidebar for my giveaway) then copy the code below and replace the writing in red sorry I couldn't place these in blogger the coding messed up and have had to place as images:
If you want to create a blog button with a grab box then copy and paste the HTML below: