While you wait for your 3.5" or 5.25" adapter to come in, you can just have the SSD connected and sitting on something that it can't short out. I usually test them in my system by setting them on top of the DVD drive. Use some tape to hold them down if you'r worried it might slip out and damage something. Now that i wrote that, I remembered the one in my server is duct- taped to the inside bottom of the case. LoL it's been fine like that for years.
[edit] When you do go to install it, remember to switch the PSU off or unplug it first. PC's are never really off when shut the OS down anymore.