Hey seems developer shine by their absence. I am working on the same theme.
1st
Go to Dashboard > Pages > Add new
Create Home & Blog Page
choose Photograph Corporate Template from Template drop down like as shown in screenshot.
2nd
go to Dashboard > post > tags > create all the tags you will be using (this will later become your categories (this is how these developers made out the theme.
3rd
go to Dashboard > post > create posts and use the feature image this image is the one that will appear in the front page, use the right sidebar to set the tags for that post, click publish.
repeat… create as many posts as images you want to see in your front page using feature image and adding them a tag.
4 – This is where tags become categories
Go to Dashbarod > Appearance > Customize > Frontpage > Select Category (Select any category you like to display. If you don’t select any then all post will be displayed)
Select tags from the tab tag dropdown to display tab section. Save and then go check your front page.
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Done!