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/bin
sudo ln -s /path/to/binary binary-name

And then run these commands?

source ~/.profile 
or
source ~/.bashrc

If you make a ~/bin folder in your home folder, it'll already be in your default path. No need to modify anything, or add folders to a hidden .local folder. Create the ~/bin folder, log out, log back in, and open a terminal window, and you can confirm the path by typing echo $PATH.

Update #1:

If you decide to use ~/.local/bin anyway, add this to the end of your ~/.profile...

# set PATH so it includes user's private ~/.local/bin if it exists
if [ -d "$HOME/.local/bin" ] ; then
    PATH="$HOME/.local/bin:$PATH"
fi

Then log out, log back in, and your new path will be available.

The PATH variable gets changed when this shell command is executed:

export PATH=$PATH:/your/new/path

The ~/.bashrc and ~/.profile will be executed automatically when you open a bash session (normally when you open a new terminal window/tab).

So if you want to change the PATH in current shell session only, you could just type export PATH=xxx and execute it once. But if you want to make it difference permanently, you should add the command above into ~/.bashrc or ~/.profile.