Not all of the chapters are online. You should be able to burn them to a disk from your unit, that would be the easiest way. If you just type NSTM in google, you will get links to the chapters avaliable online. This site has some of them: fas.org/man/dod-101/sys/ship/nstm/index.html
The DC related NSTM's are also available on the CGCentral page for Training Team East/Atlantic Area Force Readiness (Axr). This is only available on CG Intranet accessible computers.
Just sign-up for a Navy Knowledge Online (NKO) account. It's free and all the NSTMs are available under the "Naval Engineering Forum" page. Once you have a NKO account you can access the NSTMs via the Internet or CGDN. Shoot me and e-mail if you need assistance.