How do I remove a bookmark?

Go to the world map screen and tap on the bookmark icon to the left of the co-ordinates to open the bookmark list. At the bottom of the list is a cog icon, tap this. You can now select any of the bookmarks you have and then you will have a 'trash' or bin icon at the bottom that will let you remove them.

Alternatively if you are at a book mark location and tap on it to bookmark it again then you will have the option to Modify the bookmark and also a trash icon at the bottom left to remove it from your list.