The first time I ever installed a muffler, it took a few days because I had to get the right muffler and an exhaust cutter(A saw could work too). The muffler I was getting was a cherry bomb. I tried to use an exhaust adapter so I didn’t have to find someone to weld it on. For some people, you can use the right size exhaust adapters and the right brackets, but since it’s not welded on, your pipes will be messed up if your muffler breaks or falls off. That’s why I asked my buddy to weld it on. You’re also going to want to let it run if you’re doing the brackets because it will have to go through heat and the bolts will come loose so you just need to keep letting it get hot and then tighten the bolts and brackets till they don’t come loose anymore. If you weld, let it run, and do the same for bolts if you go with the cherry bomb because it has a break-in period.