source activate myenv # (in linux, you can use . as a shortcut for "source")
activate myenv # (in windows - note that you should be in your c:\anaconda2 directory)
source activate my_env # activate your target env with spyder installed
conda info -e # look up the directory of your conda env
find /path/to/my/env -name spyder # search for the spyder executable in your env
/path/to/my/env/then/to/spyder # run that executable directly