Not sure if this is what you ask but:
- if you owned e.g. 1 mil NOBLE at the time of switch (in this case just before the test blockchain was started) you can access same amount on PoS wallet. you just need to follow the docs -> last paragraph of https://github.com/eagleflies/noblecoin/wiki. any further purchases or sells are not going to affect your balance on test blockchain
- you can also ask someone to send you some funds on test network. just provide your address

Happy testing!