To replace some hardware, you'll have to schedule a replacement job. To do this find the 'Network' section, click through your Organisation to the relevant Venue and find the Spot you need to amend in the 'Spots List'.
Click on the wrench icon and choose the 'Replace' option.
To mark your Spot for replacement, make sure that there aren't any other current Jobs for that venue that aren't in the 'Preparing' state. Make sure you change the stage of any other active Jobs to 'Preparing' or 'Complete' using the buttons so this is your only active Job.