Non Fidelity funds - Vanguard funds

After converted to Fidelity IRA, had to sell all non-Fidelity funds I owed such as Vanguard Total Stock fund and Vanguard Value Index fund.  I am thinking to put it on Fidelity 500 Index and Total Bond funds.  Should I put it one time or $50,000 now, then add more later?    I know no one knows how market is going to be in the future, but I just want to low my risk.  Thank you.