Original Becker Question

[DrewGerhan]

I have a 81 300SD and it has the original Beacker radiow/ cassette player. The radio works fine but I cannot insert a tape into the deck. I pushed open the door and saw that there are the two red things sticking down that spin the cassette in the way. Anybody have any ideas on how to et those things up? Also I cant figure out what the buttons mean or what they stand for. Could there be like an insert tape button? Thanks in advance.