Joining the club is easily done online via either the British or Scottish Orienteering website. Note that for liability insurance purposes you must join one of them, club-only membership is only available if you’re already a paid up member with another club (and therefore are already a BOF or SOA member).
You have 2 options: Option 1: Join Roxburgh Reivers, Scottish Orienteering and British Orienteering in one. Annual fees are very modest – £19 for seniors, £3.80 for juniors (as at Jan 2018) http://www.britishorienteering.org.uk/page/join_online
Option 2: Join Roxburgh Reivers and Scottish Orienteering. A bit cheaper (£9 for seniors and 50p for juniors) and a good choice if you just want to orienteer in Scotland. A £2 levy will probably apply if you go to any English events. Details here
More detailed comparison of the 2 schemes HERE
Email: firstname.lastname@example.org if you have any questions.