Open a new Terminal window and go to your home directory (just type
cd and press Enter).
After that, type
ls .bash* and also
ls .profile (please note each of those file names starts with a dot). If you have those files (and you should have at least the .profile one) then you need to edit them and add your aliases to them. I use VI (or VIM) to edit those files, but you could use another editor (in fact typing in your Terminal window
open .bash_profile will open it in TextEditor, which may be a bit more user-friendly if you're not familiar with VI). If, for some reason, you don't have any of those files, then create a new one (and call it .bashrc), add your alias lines into it (so this will be one command per line, as you would type them in shell) and then save the file. You can then create symlinks to .bash_profile and .profile by using
ln -s .bashrc .bash_profile; ln -s .bashrc .profile.
What I typically do is I make .bashrc and .bash_profile symbolic links to .profile and then just have to worry about one file only.
The difference between those files is that bash will source different ones depending on whether it has been started as a login shell (typically a login process would start the shell as a login shell) or as just an interactive (but not login) shell, or a non-interactive shell. Having all three files essentially the same gives me consistent environment regardless of how was bash started.
You will get more information by doing
man bash, but be prepared, it's a long man page. You will be able to see which of the three files (.bashrc, .profile and .bash_profile) is sourced depending on which mode was bash started in.
Hope that helps - if not, give me a shout.