open terminal

$cd ~

$open -a TextEdit .profile

In TextEdit

# MacPorts Installer addition on 2009-10-28_at_16:24:44: adding an appropriate PATH variable for use with MacPorts.
export PATH=/opt/local/bin:/opt/local/sbin:$PATH
# Finished adapting your PATH environment variable for use with MacPorts.

Add new path in export PATH like this

# MacPorts Installer addition on 2009-10-28_at_16:24:44: adding an appropriate PATH variable for use with MacPorts.
export PATH=/Applications/MAMP/Library/bin/:/sw/bin:/opt/local/bin:/opt/local/sbin:$PATH
# Finished adapting your PATH environment variable for use with MacPorts.