Selecting swashes in Font Book
If you are using Font Book, select the font you are interested in from the list, and change the View to Repertoire (View>>Repertoire).
Font Book Video [for Mac] by Laura Worthington
Finding swashes in Character Map
In Character Map, Windows sometimes switches the font to a default font for some strange reason, so double-check that your font is chosen from the drop down menu. Click the Advanced View checkbox at the bottom of the Character Map window and select Character set “Unicode” then select Group by “All” to see everything in the font, or Group by “Unicode subrange” then select "Private Use” from the pop-up box to see just the special characters.
Character Map Video [for Windows] by Laura Worthington
Tips for using PopChar®
Find the alternates in the Private Use Area tab. Make the glyphs larger by clicking on the gear button in the upper left corner of the pane. Select Preferences, then View & Insert. There is a slider at the top of that pane that will allow you to control the size of the glyphs.