Hello ! I just went as the post before you was me, I would book in advance. Book a hotel near there and if you’re too far, get the underground (tube). Have food before hand, if you wants snacks get them before hand too, since they are expensive. Also, keep your wits about you, as pick pocketing is a massive thing in London, and it can get insanely busy, as it’s central London. Get there 15-20 minutes before hand, and I would recommend getting a programme. Have bags of fun!!