Presets are editing settings (slider values among others) which are saved to be reused with other pictures.
I imagine you are asking about saving the ACR settings of an image.
When you edit an image in ACR, clicking either 'Done' or 'Open', the settings are stored in an xmp sidecar file (raw files) or in the metadata header of the file itself (jpeg, tiff, psd...)
The settings for the last edited files are also saved in the organizer.
To use the settings of a file you have edited before, open that file in ACR, change slightly the value of a single slider. The settings are now saved as the 'last edit' settings. You open the file to which you want to apply the settings and you choose 'last edits'. You could create a personal library of files saved in a collecdtion or folder to be used to store many kinds of corrections or special effects.
Note: if you have raw or DNG files produced with the full ACR version or LR, all the settings including those not available in the Elements version are saved and usable in the 'last edit' choice. You won't be able to edit them, but you could create a library of presets for LR or PS ACR by storing files with those presets applied.