how to appeal pip decision

hey guys so I got my letter in and was given 8 points standard rate when I was on higher rate ive went through the points scoring and I should have been given 12 points mainly due to her either lying for some of my points that I clearly did not say or due to her English not being that great and my aniexty being bad maybe that was the problem or maybe I too naïve, the annoying thing is I brought a family member with I asked to record the interview I thought she had recorded it but when we got out she says it didn't work but I take it if it goes to tribunal I can use her as witness to what I said etc?  anyways how do I go about appealing this guys as id like to appeal and what usually happens if anyone has gone through this before, I wont go through all my points etc I just need help on how to appeal and any advice on what to expect and what happens after if this fails and if I appeal this decision is there a possible I could have all my benefits stopped I really don't know enough on this, there is not enough info on the letter, any help would be great.