To make a script to replace a phrase use the ::abbreviation::
hotstring syntax. It will replace btw
with by the way
whenever you enter btw
and then the space key.
::btw::by the way
If you wanted to make a login script to make logging in faster you could make a script like this (the file is not encrypted so any information in your script will be visible to anyone with access to the file).
::lmi::user{tab}password{enter}