Step 1 - Get a latest version of zncstrap. Install Git / Git Core on your Linux machine or alternativly, install and use wget or aget tool; or the good ole way via FTP/sFTP.
Step 2 - We strongly advice you to make backups of your current files/folders before you proceed to install zncstrap. Once you have your backups stored elsewhere, you can proceed to delete/remove the default theme(s).
**Q: Why can't zncstrap work alongside the default ZNC themes itself?**
A: Mainly because the different HTML tags and attributes used in zncstrap, as part of Twitter Bootstrap specifically in "~/znc/share/znc/modules/webadmin/tmpl" (e.g http://git.io/qj8MKg to http://git.io/SofsZg). If it had been left un-edited, it will not be visually pleasing and would be looking all off-margin. As the CSS bits are different and varies. Hence why the default ZNC themes should be removed as it will no longer serve any good when zncstrap is installed.
**Q: I installed zncstrap, but it is off-margin and un-styled!**
A: You should overwrite everything from '~/zncstrap/modules' to "~/znc/share/znc/modules" on your machine.