Aerating your lawn has many benefits. It can increase drainage, it can help get nutrients down to the roots, and is great before seeding!
You’ll need to rent an aerator, it’s best to use a core aerator although some use a spike aertor. The reason I prefer the core plugger is because it creates larger holes which means the benefits last longer as the soil settles.
When you aerate, you’ll want to go over the yard multiple times, in multiple directions. Many will do a pass going north/south then east/west. But it doesn’t have to be that way, you could go the same way just multiple times. The plugs are arranged in a way where it’s not important exactly which way you go.