You can hold them anywhere (with one exception, exchanges that are not configured to receive/withdraw SingularDTV dividends)
You can then use for example MEW to withdraw the dividends. (instructions will be here also, once the first dividend is issued) These dividends are based on the current amount which you are holding SNGLS on the time SingularDTV issues dividends. It was said that this would become everyday operation in the future..

For example:
Binance is configured to allow this rewards collecting and hold those SNGLS in Binance.
https://medium.com/singulardtv/binance-to-support-all-future-sngls-airdrops-no-need-to-move-your-sngls-ccfe036c8a0