Everything you need to know about using Ebay, including how to retract a bid, is in the Help pages with their integral search (links at top and foot of any page).
There are very few reasons indeed for a valid bid retraction (when you bid, you enter into a legal contract with the seller). Bid retractions are marked on your feedback page for all to see and act upon (most sellers won't deal with buyers who've retracted bids in the past). So don't bid in future unless you're 100% sure the item is what you want, after you've carefully read the description, and that you can pay for it.
@steviedee1st
