A specific tissue preparation protocol is not included with this kit. Product C3228, CelLytic MT reagent for mammalian tissue, is suitable. Please see the link below to review the product datasheet and protocol:
https://www.sigmaaldrich.com/deepweb/assets/sigmaaldrich/product/documents/317/238/c3228bul.pdf
Flash freezing the sample in liquid nitrogen and cold homogenization methods are also suitable for use with this kit. There are a number of methods available in published literature. Please see the link below for articles that may be helpful:
https://scholar.google.com/scholar?q=tissue+lysate+protocol&hl=en&as_sdt=0&as_vis=1&oi=scholart