Hi Fiona and welcome to GoY. Is your tree in the ground or in a pot? I don't know about monkey puzzle trees in particular, but when I plant trees in the ground, in general I just water well for the first year (i.e. soak them weekly if we haven't had any rain in that time.). I think they need to get good root growth going first and as deep as possible which is why it's a good idea to incorporate some blood fish and bonemeal into the soil when planting. They provide slow release nutrients in the area where you want the trees roots to go.

I'm not that scientific or precise about feeding and just chuck slow release fertilizer round the garden generally in spring, hoping that any plants in need will help themselves. I'm sure the experts on here are shuddering! ;-)

If it's in a pot it's totally dependent on you and its roots can't go down as they should, so you'll have to water very carefully. Maybe feed a little bit next spring with those slow release fertilizer granules....