I can tell you general procedure for RNA, it should apply to microRNA too. Take tissue out from animal or from subject and directly place in RNAlater in a sterile tube. With sterile scalpel in a sterile dish on your lab bench, cut tissues 1-2mm in thickness. Than pour back tissue pieces in the tube (all steps dipped in RNAlAter solution). You can transport the tube for 1/2/3 days at room temp. Or for more time transfer or storage in Liquid nitrogen (transfer contents in cryovials). You can read instructions comes with RNAlater bottle. If further question, call the company toll free number.
I agree with Subhash, i have used RNAlater to conserve both samples (gut, liver, spleen...) and extraxcted RNA and i have got good results. knowing that i put immediatly the organ in the solution of RNAlater and let in freezer almost 6 months and then in ambiant temperature for 3days, then one month at 4 degree!! and the results were good.