I have already given a simple tutorial on how to import assets with MIF using interface tables. Now, if you want to import asset specifications as well, this is a detailed tutorial on how to do that with interface tables. You can also download a sample excel document that I used to import into the interface table, prior to the MIF importing into Maximo, which you can use as base structure for your own data import.
Prior to loading data, I will assume that you have already setup the MIF, entered locations, and created some classifications for your assets. To setup MIF that is ready to import assets you can read this post.