A bit vague for my knowledge at this instruction, If I make them not writable I will not be able t do the installation.
But What About Shared Hosts?
With some shared hosts (for example, if your only access is via CPanel or a similar web-based admin tool), you may not have the ability to change the file ownership, and your webserver is effectively running as your user. In that case, you may still have the ability to protect your files by making them non-writable by your own user (even though this sounds counter-intuitive). In a shared host, you will almost certainly want to deny world permissions to your files, but look to the documentation and support for your host in particular.