I tried this link but in step 5, I am not able to edit the newform.aspx.I am not able to add the spservices
code there, it seems like the codes there can not be edited.
2 Answers
Create a new newform and try there. The default one works a little differently. After changing you can make the changed forms The default new/edit form.
Alternatively when in the browser go to the list menu and find the form edit buttons. Click the form you want to edit and add a content editor webpart to the bottom. Either link to the JavaScript in a file or enter it there manually.
Advanced Mode
or not. Advanced Mode button can be found in ribbon.