I suppose given the apparent lack of knowledge about what is inside your "cranks" that the obvious question is what is it doing that makes you think it needs greasing?

Sorry but your question is disconnected in so many ways that it's somewhat obvious that you don't know what the arrangement is of the bearings and the fact that there are many different styles of bottom brackets and crank systems and they all have slightly different needs.

You can fill yourself in by visiting the Park Tools repair website at http://www.parktool.com/repair/ and hover your mouse over the cranks and then click to learn more about the different bottom bracket styles and how to service them. And regardless of which you have they ALL require at least some disassembly to service them. And if it is one of the sealed cartridge style bottom bracket then you don't service them. You replace them.

PS: when you said "grease or lube" I gather you meant to say "grease or oil" since "lube" is any form of oil, grease, wax, powder or other lubricant that makes things slippery. It's not a "product" on it's own.