Hey there! Good question.
Keep in mind, we started these portfolios with a baseline of 10k, but that full amount isn't all in stocks. For example, our Millennial Conservative portfolio Contains 57% equities, while our Millennial Aggressive portfolio is 80% equities. We'd suggest putting the remainder into fixed income investments or even ETFs that could give you international exposure.
However, with fixed income investments taking a beating because of low interest rates, you'd be wise to figure out your overall risk tolerance and see if you'd be comfortable putting a heavier allocation towards stocks/ETFs. That is ultimately up to you though.
The easiest way to go about it would simply be to take the initial investment and figure out the percent allocation. If you let me know what portfolio you're looking at, I'd be glad to do it for you and post it in here.