You need face to face welfare rights advice.
In the first instance you have 28 days to request a statement of reasons (the full decision with reasoning, written by the judge on behalf of the whole panel, but only when you request it) and the record of proceedings (the handwritten record of proceedings taken by the judge).
Once you have the SoR and the RoP you need that welfare rights advice to identify one of the five possible errors of law.
Almost all decisions have errors in (I've literally found only 1 decision in 31 years in advice work where I had to hold my hands up and say I couldn't find one) and often there are multiple errors but you need someone used to looking for them as it's easy to confuse a dispute about the facts with an error of law. You cannot appeal on a point of fact. The facts only get determined at first tier tribunals. Upper tribunal can only look at whether they got the law right.
So, as well as looking for errors of law any decent WRO will also be weighing up what you would get if the case was won at UT and returned for a fresh hearing at a FTT. We often have to advise people that whilst their FTT decision could be taken to UT won and returned to a new FTT there is no point if the outcome would be no better or worse in our view.