First find the wine

WineBase has all sorts of search options that make finding a wine or wines really easy. What search method you use depends very much on the wine you're trying to find.

As a last resort you could just use this button to list every wine in the cellar or the View - Index Listings - All Wines in Cellar menus.
But it's probably better to narrow the search by using one of the more popular search option buttons on the WineBar or failing that the dialog that includes them all.
Search and Sort options dialog...
Which will be listed here

In this rather stumpy Index Listing and as it says on the bottom right hand corner of the window Left click to View or Right click to Edit

The click is a mouse click, left and right is which button on the mouse and you click on the wine itself.

If you Left click on the Vintage for a wine (Vint column) a popup menu will appear offering various options, one of which is Delete this Wine

Warning There is no undo on this, once a wine is deleted it's gone.