Re-reading your .bash_profile When you make a change to your .bash_profile it will be read the next time you open a terminal.  But what if you have a terminal open already. Is there anyway to do a re-read?
You can use source

source ~/.bash_profile


From the bash manual:


    .  filename [arguments]
   source filename [arguments]
          Read and execute commands from filename in the current shell environment and return the exit
          status  of  the  last command executed from filename.  If filename does not contain a slash,
          file names in PATH are used to find the directory containing filename.   The  file  searched
          for  in  PATH need not be executable.  When bash is not in posix mode, the current directory
          is searched if no file is found in PATH.  If the sourcepath option to the shopt builtin com-
          mand  is  turned  off, the PATH is not searched.  If any arguments are supplied, they become
          the positional parameters when filename is executed.  Otherwise  the  positional  parameters
          are unchanged.  The return status is the status of the last command exited within the script
          (0 if no commands are executed), and false if filename is not found or cannot be read.