conda update

# Basic syntax:
conda update packagename # To update specific package in the current env
conda update --all # To update all packages in the current environment
conda update -n myenv --all # To update all packages in myenv environment

conda update --all

# If want to update python type
conda update python

# To update anaconda type 
conda update anaconda

# a) If you want to upgrade between major python version like 3.5 to 3.6, you'll have to do
conda install python=$pythonversion$

# b) Method 2 - Create a new environment (Better Method)
conda create --name py36 python=3.6

# c) To get the absolute latest python(3.6.5 at time of writing)
conda create --name py365 python=3.6.5 --channel conda-forge