Are you wanting the latest in the 1.0 series (1.0.54 vs. 1.0.24 which probably isn’t much of a change)? Or the latest development of psi4 (~1.1rc1)?
If the latter, there have been so many structural changes that you don’t want to update, you just want to fresh install into a new environment.
conda create -n p4env python=x.x psi4 psi4-deps -c psi4/label/devel -c psi4
Same for Mac/Linux. Substitute desired python version: 2.7, 3.5, 3.6. Only reason for psi4-deps is to get the qc runtime addons; could say “dftd3 gcp v2rdm_casscf” instead of “psi4-deps”; or leave them out if you don’t want them. Activate environment and make the adjustmets to PATH and PSI_SCRATCH that it suggests at the end. Test with psi4 --test.