This is how you do it:
git stash push -m "my_stash"
Where "my_stash" is the stash name.
Some more useful things to know: All the stashes are stored in a stack.
Type:
git stash list
This will list down all your stashes.
To apply a stash and remove it from the stash stack, type:
git stash pop stash@{n}
To apply a stash and keep it in the stash stack, type:
git stash apply stash@{n}
Where n is the index of the stashed change.
Notice that you can apply a stash and keep it in the stack by using the stash name:
git stash apply my_stash_name