How to set up adb environment variable on Mac

set up adb on Mac

// Step 1. Open or create the .bash_file
// Open .bash_file
$ -a TextEdit ~/.bash_profile 
// create the file if it doesn’t exist: 
$ touch ~/.bash_profile

// Step 2. Add path to adb tool (note your path maybe different)
export PATH=$PATH:/Users/Margaret/Library/Android/sdk/platform-tools/

// Step 3. Make the new path in effect
// Close and reopen terminal if typing “adb” command not yet working.
// Reload the environment variables (if needed). Note there is a space after the 1st dot
$ . ~/.bash_profile 

// Step 4. Verify the path update is successful. 
// You should see your adb version; otherwise check the path in your .bash_profile
$ adb version

still i get error ,.bash_file does not exist.
What should i do?