Starting at 0% you can just up throw similar to how marth does. If you don't want to do that you can LK grab. At 0% do a forward throw then immediately do a down throw after. They won't be knocked down from the forward throw so you can run in and grab again right after. They can buffer a spot dodge but you can just wait a little if they start to do that, most people just shield so it's a free grab. Most times if you do the fthrow -> dthrow real fast they won't tech it so dtilt the missed tech.
After getting the grab and starting the chain grab just up throw til about 35%. At this point you will need to up throw -> up air -> regrab or they can shine out of it. at about 45%-50% if they DI hard to the left or right you can catch them with a dash attack -> regrab. at 70% is when you want to do up air -> fsmash. After about 80% they can jump out of it so you will have to do a quick double jump up air -> short hopped up air -> fsmash. After about 95% you can't do anything after up throw. Though at 120% ish if they don't DI a down throw in you can get a free fsmash.
That's a basic overview of it. Just let me know if you have any more questions about it.