How can I remove one of my glossaries?

Go to the personal glossaries section. Search for the glossary you want to remove on the list of glossaries under "My glossaries" (on the right page column).

Click on the small delete icon next to the glossary name. A window will pop-up allowing you to confirm the removal:

Are you sure you want to delete this glossary? All entries within the glossary will also be deleted. This action cannot be undone.