Both CATs are present in the front side of the vehical.
The removal of 1st CAT is very easy, just need to remove the manifold and get the CAT out.
The removal of 2nd cat takes a bit longer, first you need to get the exhaust piper out, from just after the manifold till the silencer, there are two dholkies in that pipe, the dholki near to the front side has CAT, in order to get the CAT out you need to cut that dholki and get the CAT out after that you need to take it to welding guy who welds the dholki and bring it back to original position.
If you read this with all the pics which i have attached, you will understand better.
Hope i have explained well.