Use different Anaconda environments on Linux Mint and Spyder

[StaLLoNe_CoBRa]

I'm trying to use and install packages in more than one environment through Anaconda 4.9.2 (I use Linux Mint 20 and Spyder 4.1.5). I created an environment called phdenv, and it seems to me that I was able to install Python 3.7, but when trying to activate the environment through the command

conda activate phdenv

the error that appears is the following:

CommandNotFoundError: Your shell has not been properly configured to use 'conda activate'.
To initialize your shell, run

     $ init init <SHELL_NAME>

Currently supported shells are:
   - bash
   - fish
   - tcsh
   - xonsh
   - zsh
   - powershell

See 'conda init --help' for more information and options.

IMPORTANT: You may need to close and restart your shell after running 'conda init'.



Note: you may need to restart the kernel to use updated packages.

what am I doing wrong?