Use these steps:
1. Select 'New Profile'.
2. Give the profile a name (can be anything), and under 'Use Version:' select the drop down 'release 1.6.2'. Then click 'Save Profile'.
3. You will notice your new profile will appear under the 'Profile Editor' tab, but it will say you're not logged in. So under profile, select the drop down 'angelsrage21' (or whatever you named your profile)
4. Now with your new profile selected, enter your username and password, and tick the 'Log me in automatically' box. Then click 'Play'.
5. Now every time you open the launcher, it will remember those credentials under that profile only. And it will simply say 'Log Out' and 'Play', so just hit 'Play'.
Good luck, hope this helped.