Who did you book with? Normally most companies offer advice about what to do. Make sure you pay attention to the timing of the PCR some countries it’s 72hrs before departure some 72hrs before arrival.
antigen test is just lateral flow but you normally can’t use NHS ones, ours we just took a picture of the result and uploaded it and we were good to go. Same on the one to return to the UK, I think @tonyh29 and @SuperTed had to do a video call.