How do I set up an account for an Opportunity Zone Investment, it is a tax advantageReal Estate Fund

An Opportunity Zone "investment interest" can take the form of an equity interest, including preferred stock or a partnership interest with special allocations - in other words, investors are either shareholders or partners.  In Quicken such an ownership interest could be entered as a "brokerage account" in the Investing tab, with a single investment in the partnership/corporate entity at the investor's initial cost/basis.

Obviously, you won't be able to download prices, and will need to manually record price changes (values) and other transactions (such as distributions) over time as such information is provided to investors/holders by the entity.  However, given that these entities are organized for the primary purpose of delivering tax advantages/savings, and the fact that the underlying real estate needs to be held for a number of years (at least 10 years in most cases) in order to qualify for those tax advantages, I suspect that there will be little activity to record in most cases.

Hope this helps.