I hope these steps will help you:

1) Download the Amber20 source code from the Amber website.

2) Extract the Amber20 source code to a directory of your choice.

3) Navigate to the Amber20 source code directory and run the configure script with the following options:

"./configure -cuda /usr/local/cuda"

4) compile Amber20 by running:

"make -j"

5) you can install Amber20 by running:

"make install", will install Amber20 to the default location /usr/local/amber20

6) you will need to set the environment variables for Amber20. Add the following lines to your .bashrc file:

"

export AMBERHOME=/usr/local/amber20

export PATH=$PATH:$AMBERHOME/bin

"

Remember to source the .bashrc file or open a new terminal to apply the changes.

That's it! You should now have Amber20 with CUDA installed on your Ubuntu 20.04 system.