How can i find the AV button on my tv remote control. ?

I bought a brand new set top box Alba STB2 and followed the instructions to the letter. i.e AV1 SCART LEAD from TV goes to the single scart socket on set top box. AV2 scart from TV goes to single scart socket on dvd player. TV ariel goes in to back of set top box. and the RF out ariel goes in to ariel socket on tv. Then i press red button on remote, light changes from red to green, to start searching channels and nothing happens!

The instructions then tell me to press AV button on remote, to start the channel search, but i can't find it. The TV is a sony 7 years old works perfectly model KV29X5L.

Please help me to set up set top box which is brand new.

Look forward to your reply.