First off, welcome to AA! I would think to some extent smell might work, but I would never trust that alone. Test for amonia and nitrite, it will cycle just like just like a new tank w/ amonia spiking then nitrite spiking as amonia goes down them nitrite dropping to zero when it's fully cured and ready for the display tank. If it was cured at your LFS
and you just brought it right home it should be fine. Most people experience die off and have to cure LR
when they get it mail order.