Someone give me a nudge in the right direction?(Tower Defense)

Shenanigans Studio

Key info:
Top down
not set path
Grid style
Towers and enemies will be spawned

Best approach:??
-constrain enemies position to a table to let towers reference
-make a table that represent map (10x10) each cell represents a spot on map and when enemy is in the cell make that cell in table active.
-other ___________ ?

the first two were just ideas that first came to mind, haven't planned out the exact details of either.
All tips and advice would be greatly appreciated!