You guys are a tough crowd.

Ablang your World Sport is an older bike I'm assuming. It may or may not have a cartridge bottom bracket. If it does, then you replace the whole cartridge. If not, then it's either got loose ball bearings or ball bearings in some sort of retainer. Either way, they should be replaced with new ones. You'll also need to clean and re-grease.

Doing this requires that you remove the cranks (needs a special tool) and disassemble/remove the bottom bracket itself. There are also special tools used for removing bottom brackets and the tool(s) you need depend on the type of bottom bracket you have. The Park Tool site that somebody else recommended is a great resource as well as Sheldon Brown's site.

The easiest thing to do of course is to bring it to a bike shop. There are bike co-ops that will allow you to work on your bike and use their tools for a fee if you want to do it on your own without buying the necessary tools. Many of them also hold classes on bike maintenance.

Personally I think it's better to have had experience repacking the hubs on your wheels before tackling a non-cartridge bottom bracket. It's not like it's terribly difficult if you're mechanically inclined but ball bearings spilling out of your bike can be a bit disconcerting.

Good Luck.