How do I add a Item type like lawn mowers so I only get one not 2 or 3

Hello Graeme,
Thank you for your question about Bid Groups. To add items to a group, use the "Add Snipe" box on your dashboard, and then select "New Group" from the pull-down. Any items you place in a group will be turned off as soon as you win an item in that group.
Here is our help page on that subject: https://bidslammer.com/help/bid_groups
Thank you for taking the time to write in. Please let us know if you have any other questions. We are happy to help.