You don't. The points you see after user names here in the Community are from a counter that BG uses to keep track of those who are active in the Community. You can up your point numbers by "liking" a question or answer or by posting one yourself, or by answering someone else's. We don't get any "perks" for having a high point value, and it doesn't really matter to me and a lot of others.
For transcribing, the BG systems keeps a count of the number of transcriptions you do by month and by total number done. You will see these numbers in your Dashboard profile.
Contribute to BillionGraves and you can receive FREE access to BG Plus features. Every month that you upload 2,500 or more photographs or complete 500 or more transcriptions you will receive credit for one FREE month of BG Plus.**
If you are a real beginner to BG, take some time to read the FAQ (link at bottom of Dashboard Page and also the numerous FAQ here in the Community (mainly written by Grave-Digger over the past year or so.)