improve conda installation in the documentation (#1808)

Fix #1806. Fix #1792.

Signed-off-by: Jinzhe Zeng <[email protected]>

doc/install/easy-install.md

@@ -19,23 +19,28 @@ Some packages are splited into two files due to size limit of GitHub. One may me
 cat deepmd-kit-2.1.1-cuda11.6_gpu-Linux-x86_64.sh.0 deepmd-kit-2.1.1-cuda11.6_gpu-Linux-x86_64.sh.1 > deepmd-kit-2.1.1-cuda11.6_gpu-Linux-x86_64.sh
 ```
 
+One may enable the environment using
+```bash
+conda activate /path/to/deepmd-kit
+```
+
 ## Install with conda
 DeePMD-kit is avaiable with [conda](https://github.com/conda/conda). Install [Anaconda](https://www.anaconda.com/distribution/#download-section) or [Miniconda](https://docs.conda.io/en/latest/miniconda.html) first.
 
 One may create an environment that contains the CPU version of DeePMD-kit and LAMMPS:
 ```bash
-conda create -n deepmd deepmd-kit=*=*cpu libdeepmd=*=*cpu lammps -c https://conda.deepmodeling.com
+conda create -n deepmd deepmd-kit=*=*cpu libdeepmd=*=*cpu lammps -c https://conda.deepmodeling.com -c defaults
 ```
 
 Or one may want to create a GPU environment containing [CUDA Toolkit](https://docs.nvidia.com/deploy/cuda-compatibility/index.html#binary-compatibility__table-toolkit-driver):
 ```bash
-conda create -n deepmd deepmd-kit=*=*gpu libdeepmd=*=*gpu lammps cudatoolkit=11.6 horovod -c https://conda.deepmodeling.com
+conda create -n deepmd deepmd-kit=*=*gpu libdeepmd=*=*gpu lammps cudatoolkit=11.6 horovod -c https://conda.deepmodeling.com -c defaults
 ```
 One could change the CUDA Toolkit version from `10.2` or `11.6`.
 
 One may speficy the DeePMD-kit version such as `2.1.1` using
 ```bash
-conda create -n deepmd deepmd-kit=2.1.1=*cpu libdeepmd=2.1.1=*cpu lammps horovod -c https://conda.deepmodeling.com
+conda create -n deepmd deepmd-kit=2.1.1=*cpu libdeepmd=2.1.1=*cpu lammps horovod -c https://conda.deepmodeling.com -c defaults
 ```
 
 One may enable the environment using