Those insects do look like Giant Conifer Aphids.  Their populations tend to being highest in late spring, but since the tree is small enough for you to still reach the branches, hosing them off is an excellent management strategy.  You may have to repeat the treatment several times to take care of them.  If you don't mind squishing insects, you also can simply run the branches through your gloved fingers and that will wipe out a lot of them.  If you would rather resort to a pesticide, use either an insecticidal soap or a systemic pesticide, just be cognizant of the fact that the systemic will kill non-target insects, as well as the aphids.  Here's some information about Giant Conifer Aphids from the Utah Extension:  

https://extension.usu.edu/pests/ipm/ornamental-pest-guide/arthopods/aphids-adelgids/giant-conifer-aphids

Fall planting of conifers sometimes leads to stress because with their limited root capacity it can be a struggle to uptake sufficient moisture through the winter, and a stressed plant is more susceptible to pests and disease.  Check that the plant is getting enough water at the root ball, given its site.  You also could ask a certified arborist for an on-site evaluation to recommend a management strategy.