Choosing your template/container couldn't be easier - in fact there are 2 ways to do it.
Choose your container from the drop down list from with in the add/edit interface, or select the "Custom Template" option by clicking on the block once it has been added to the page.
There are 3 ways to add images to your container.
You can use the 2 built in image selectors from the "images" page within the editing interface or actually add one to the body of your container using the TinyMCE editor. If you wish to align your images then using TinyMCE is probably the option for you.
When customizing your container it is worth noting that the styles that are applied are often dependent on the container you have chosen. For example on the "Speech Bubble" containers any border set will be applied underneath the title; conversly a border set on the "Rounded" container will apply a border around the whole content/description area.
If you want to remove/hide the border on say the "Speech Bubble" container then you should set the border color the same as the main background color.