navigate to your desk top
Click sort by type (should put all your photos together)
Now click and hold while scrolling to select all of your photos... (use the right button on your mouse)
after selecting all of your photos you don't want, left click inside the selection and click "delete" from the menu

You might want to do this for a few hundred at a time.

Everything from the recent import should be together. Select the first one in the list, then shift>select the last one on the list. Everything in-between should also be selected. The right-click (or control click) and a menu should pop up with the option to "Move to trash." Do it. Provided, that is, that you actually want to move them all to trash. If not, you can also create a new folder and move them there.

there you can list files by name, date, etc. instead of as icons which will help things go faster.

Use shift-click to select a large number of files at a time (better than click-and-drag when your Mac is sluggish) and use command-delete to move them to the Trash (same reason).

Hope that's enough.

I took Atman's suggestion and opened a finder window so i could pick and choose images. About 80% of the images were from my trash that I have been very lax in deleting. What would cause my trash to all appear on my desktop? Anyway, I will be deleting my trash regularly.

What's a good program to clean up your Mac? I'm running 10.13.4 OS High Sierra but my computer is about 6 yrs old.

Thanks

I use MacUpdate.com to find proper versions.

Onyx is big. Read carefully.

Don’t choose every option for cleaning, especially cookies.