There is no need to “claim” BTG - if you held Bitcoin before the fork, you also hold Bitcoin Gold after the fork. You don’t need to do anything to hold it, and there is no “expriation.” (Only scam sites say that.)
But many will want to access that Bitcoin Gold; Aaron van Wirdum, probably my favorite Bitcoin writer at the moment, just published this piece:
https://bitcoinmagazine.com/articles/beginners-guide-claiming-your-bitcoin-gold-and-selling-it/
Solid advice and worth a read.