Computational: Rate of Adsorption/Desorption

Hello

I am working on modelling ethanol oxidation. I have determined my reactions and am wondering how to obtain the rate of adsorption and desorption for my species (ethanol, acetaldehyde, acetic acid, C02, and CH4). The software that I am using, Material Studios 6.0 with the Kinetix module, requires I give either a rate or Arrhenius expression. Since I am going with the Arrhenius expression I have to define the pre-factor and the activation energy. I understand I can either use kinetic gas theory or transition state theory to represent my pre-factor, but I am completely lost on how to obtain the activation energy (reading journal articles they typically just declare the activation energy and I don't know how they obtained it). Could anyone explain to me how to determine the adsorption/desorption rates of my species please? or point me in the right direction? Thank you so much for your help and time!

~K.F