在我的新Wordpress安装中无法导入大于20mb的.xml文件

From what I've been reading there's a way editing the php.ini file (I know the Loaded Configuration File path, but don't know how to edit it).

And there's also a way editing the .htaaccess file..

I have several Wordpress installs in my host. Each of them have a .htaccess file. I tried editing those files, but whenever I edit them, I get a server error..

Moreover I've seen I could use a Splitter, but couldn't find one for mac.

So I'm lost here, and don't wanna be hours migrating the whole site when I know it only should take a couple of appropriate steps.