getting f on leverage browser caching because

leverage browser caching
f (29)
62%

the following cacheable resources have a short freshness lifetime. specify an expiration at least one week in the future for the following resources:

https://life-asiknowit.com/wp-content/themes/nirvana/fonts/elusive.woff (expiration not specified)
https://life-asiknowit.com/wp-content/themes/nirvana/fonts/sourcesanspro-bold-webfont.woff (expiration not specified)
https://life-asiknowit.com/wp-content/themes/nirvana/fonts/sourcesanspro-extralight-webfont.woff (expiration not specified)
https://life-asiknowit.com/wp-content/themes/nirvana/fonts/sourcesanspro-light-webfont.woff (expiration not specified)
https://life-asiknowit.com/wp-content/themes/nirvana/fonts/sourcesanspro-regular-webfont.woff (expiration not specified)
https://life-asiknowit.com/wp-content/themes/nirvana/images/socials/facebook.png (expiration not specified)
https://life-asiknowit.com/wp-content/themes/nirvana/images/socials/twitter.png (expiration not specified)

any one know how to fix. i use wp super cache and it is awesome. but not effecting this.