Here's how to look at it.
You have an Asset Allocation chosen, right? If you don't, you've got pre-work to do first.
Now, this is easy. Look at your investments and if you've got a spread sheet like I have, I see my target AA right on the spread sheet. Next to those numbers, I have actual AA listed. What needs to be pumped up? If it's equities, I take my new investment money and buy equities. If it's bonds, I take my new investment money and buy bonds.
Maybe re-read the last paragraph to be sure, but can you point out anything about market highs or timing? No? Look carefully. Still No? There ya go.
Also, the market on average hits a new high every 18 days (at least for the last 100 years). So if you don't get in now, you're going to pay more later.