you can't inject models with sparkedit, you need HMT for that.
however, you can re-position things in the map with sparkedit. heck, you could even make a fortress out of logs! (don't do it)
ASPARTAME: in your diet soda and artificial sweeteners. also, it's obviously completely safe. it's not like it will cause tumors or anything. >.>
always remember: guilty until proven innocent
once it's downloaded, you'll open up the map you would like to add the model to (please, backup your maps first). then, you'll browse to the model tag you're going to overwrite. if it has multiple levels of detail, select the correct one, otherwise, if it's a first-person model, just select the first-person tag. select the model in the list that appears and click the inject button. browse to where the .obj file is you're going to use, then select it and hit ok.
if it doesn't work, you might've selected the wrong level of detail to overwrite (meaning there would be a vertice mismatch) or the new model you're using has a different number of vertices than the original.
ASPARTAME: in your diet soda and artificial sweeteners. also, it's obviously completely safe. it's not like it will cause tumors or anything. >.>
always remember: guilty until proven innocent