(Here’s how to update / edit slides in the Metaslider plugin.  Note, this instruction is intended for usage on a desktop, not mobile.
Click on any image to bring up a bigger version). 

To add slides in MetaSlider, 

…navigate to the MetaSlider plugin in your WordPress dashboard,

(probably at the bottom of the list on the left side of your screen).

<– Once clicked, the page will load your existing slidershows.   Choose the slideshow you wish to edit.

 

After you select your slideshow, you will see a list of slides.  To add a slide, click the “Add Slide” button in the top right corner .

You can then upload images, select from the Media Library, or choose specialized slide types like Layer Slides,
YouTube/Vimeo videos, or Post Feeds, then click “Add to slideshow” (lower right corner).

 

To delete a slide, click on the “X” in the upper-right corner of the slide you wish to delete. (highlighted in red.)

Click “Save” in the upper right corner to save your slideshow.