What kind of filter are you using? Usually for cherry shrimp people will use a sponge filter of you can get a small one of those along with the moss and add some tank water from your current tank the cycling should be pretty fast.
If your going with a hang on back filter you will need to cover the intake with some sponge so the little shrimp don't get sucked up to cycle it start with fresh dechlorinated water and add a little media from your current tank and let it start your cycle just like normal.
If your going without a filter completly and relying on the moss alone that can be done just add brand new fresh water that's been dechlorinated and add your moss then after its sat for a day or two add shrimp then just keep up on your water changes to keep the water clean and your shrimp happy.
Good luck with the shrimp I'm hoping to get some cherry shrimp myself here soon they are awesome