First intallatio probleme

It’s the first time I try to install Piwik but I received two message in the second page

1-Pdo_Mysql extension
You need to enable the PDO and PDO_MYSQL extensions in your php.ini file.
On a windows server you can add the following lines in your php.ini
On a Linux server you can compile php with the following option --with-pdo-mysql In your php.ini, add the following lines
More information on the PHP website.

2 -Memory limit
32M On a high traffic website, the archiving process may require more memory than currently allowed.
See the directive memory_limit in your php.ini file if necessary.

I don’t know what i need do to resolve it!!
somebody can help me?