If you want to show your images full screen:
Add a new Layout with a full screen region.
Add/upload image files to this region.
Use the timeline, shown under the canvas to drag and drop the images into the specified order.
Once done click the top menu to Publish.
Take a look at this guide here which goes through the steps on how to create a simple layout (without rotating content) but it will hopefully make the process clearer.
This guide on media durations may also be a helpful read.
You then need to schedule the Layout to your displays by adding an event.
We do have some online training courses which cover content creation and scheduling here which you can go through at your own pace.
Do let me know how you get on and I hope that this is some help to get you started 