How can I add ~/.local/bin to my PATH?

I'm just trying to follow this tutorial and set up my environment. My system is WSL Ubuntu 18.04. Here is already an answer on my question, but I as an absolute novice in Linux/UNIX don't know which variant presented there more suitable for my goal.Do I need to add this string

export PATH="$PATH:/path/to/dir"

into my ~/.profile or ~/.bashrc file?

Or may I need to accomplish the second step from the answer?

cd /usr/binsudo ln -s /path/to/binary binary-name

And then run these commands?

source ~/.profile orsource ~/.bashrc