"Local Adjustments" are listed in the drop-down menu beside the word "Effects" (My clip currently shows Custom: )
Note that in the folder that contains "Local Adjustments" you cannot have sub-folders. If you place "Local Adjustments" in sub-folders of [Local Adjustment Presets] they will not appear in this menu. Is this a possibility with your folder?
Is it possible that they are global "Develop" presets?
I did click on custom and got a drop down menu, so that is good but it looks like some of the presets are there but not all of them. I cannot figure out where or how I access the other presets...
FYI Presets are small files named with the file-type .TEMPLATE
In your computers operating system they are stored in folders appropriate for their purpose. They could be Develop Adjustments templates or Local Adjustment templates, etc. They can be copied, pasted, moved, (and deleted), like most other files.
This article has more about the location on Lightroom files- Where to find preference files for Adobe Photoshop Lightroom 5 (Some minor changes for LR6)
Your Develop Presets would be located-
/Users/[user name]/Library/Application Support/Adobe/Lightroom/Develop Presets/[preset or template filename.lrtemplate]
C:\Users\[user name]\AppData\Roaming\Adobe\Lightroom\Develop Presets\[preset or template filename.lrtemplate]
Your Local Adjustment Presets would be located-
/Users/[user name]/Library/Application Support/Adobe/Lightroom/Local Adjustment Presets/[preset or template filename.lrtemplate]
C:\Users\[user name]\AppData\Roaming\Adobe\Lightroom\Local Adjustment Presets\[preset or template filename.lrtemplate]
How did your purchased presets arrive? In a zip file?
Did you extract the template files from the zip or did an install program do that automatically?
Are they all in one folder together?
Did you copy them to the folders suggested above?
Were they Develop adjustment presets or Local adjustment presets?
Have you searched in the operating system for xxx.template files? (not using lightroom!)
When you are confident you know where the .template files are in the operating system, then we can begin to know if they are in the correct location for Lightroom to see them.
Sorry if I am making this appear more difficult, but 'understanding' is the key to getting them working.