Hi
it’s better if you link to the instructions you’re following, and tell us at which step you’re having problems.
But you can start by installing an AMP stack (apache-mysql-php), if you’re on Windows then I suggest either Bitnami
https://bitnami.com/stack/suitecrm/installer
or XAMPP
https://www.apachefriends.org/download.html (I would choose the one with PHP 7.1)
Note that the first link installs the stack AND SuiteCRM, while the second link installs only the stack, then you have to install SuiteCRM on top of it.