In order to activate Akismet plugins into wordpress blog on need to perform below mentioned steps:
1) Download the Akismet plugins.
2) Upload it under the /wp-contents/plugins folder.
3) Activate it from wordpress admin control panel.
Plugins -> click on activate on Akismet.
4) Once one click on activate plugins it will ask an API Key to activate the plugins.
5) One needs to provide API Key for the wordpress blog.
6) Enter the API Key and click on activate.