Before doing this(i.e. adding the next month to the dropdown menu) process the 1st set of photos for the month up to and including Setting the Featured Image
Go to Dashboard
Make a new page, Pages - add new
Add title, eg November 2016 Walk Photos
Click Beaver Builder (faint tab to right of Text Editor)
Choose Templates, Landing pages, Blank
Rows. Drag 1 column into centre
Click on Saved - Drag Group Galleries across
Click on the heading. Heading box appears. Delete Month 2018 and put correct month and year.
Click on +(above)
Saved - Title+Previous+Next - drag into top box
Alter Month from July to November or whatever. Save
Add the first walk on the slider and delete the Castle Combe one.
Add the first walk to the right hand side of the page.
Customise (at top) to get the new page in the menu. Main menu. Add items, pages select page, click reorder. Use Up arrow to get to the right group then side arrow to insert in right place. Save and Publish.
Put in links from this month to previous month and vice versa in the usual way.
Link the new photos to the previous photos and vice versa in the usual way.