If you have the calibri font in your system then you've to upload the font on the server and then provide the path in CSS. ofcourse you need different type format so font render perfectly on all browser.
body {
font-family: 'Calibri', Fallback, sans-serif;
}
@font-face {
font-family: 'Calibri';
src: url('Calibri.eot'); /* IE9 Compat Modes */
src: url('Calibri.eot?#iefix') format('embedded-opentype'), /* IE6-IE8 */
url('Calibri.woff') format('woff'), /* Modern Browsers */
url('Calibri.ttf') format('truetype'), /* Safari, Android, iOS */
url('Calibri.svg#svgFontName') format('svg'); /* Legacy iOS */
}