I think the uploaded file is damaged or your server can't unzip packs. Please unzip in your PC then upload the /wpforo-embeds/ folder to your /wp-content/plugins/ directory using an FTP application like FileZilla; or any other FTP program is fine also. Make sure you have not double /wpforo-embeds/wpforo-embeds/ directories nested inside each other, please correct this before you continue. Then in WordPress, go to WordPress Dashboard > Plugins, and then activate the wpForo Embeds addon.

The package could not be installed. PCLZIP_ERR_BAD_FORMAT (-10) : Unable to find End of Central Dir Record signature

 I just got the addon, now how to do I go about installation ? Any tips or help?

You just need to read the Addon description. Download the zip file go to Plugins page > Add New and upload it.

Okay got it installed, duh! Now I don't see the share options in posts or topics? Can anyone offer some advice?

wpForo Embeds addon is not a share addon. wpForo Embeds addon is designed as a core post content replacer. It checks content provider URLs and replaces to content provider view (video, audio players, social network widgets, etc..). There is no any action button on front end. You're getting share URLs from other websites not on forum page. You opens Youtube video on youtube website, then copy share URL and then just paste it in post content. All other extra steps will make it harder and inconvenient to use.

Thanks