I would suggest to reduce the particle size as much as you practically can, and then either co-compost it aerobically, or perhaps ideally, add it to a vermicompost setup.
Composting worms have a gullet like digestive tract, like a chicken, and will consume biochar the size of sand particles or smaller to grind any decomposing biomass they consume into smaller particles. In the process of passing through a worm's digestive tract, the char becomes deeply embedded in the evolving humic matter, is further ground down in size so that it easily aggregates with other evolving soil elements, and becomes coated and embedded with organic matter. It's pH will be neutralized, as worm castings tend toward being slightly acidic.
A few commercial vermicomposters add biochar to their worm feed, and there have been some research showing that biochar significantly increases composting worm populations and particularly worm cocoon production. There is also research indicating that worms in the Amazon consume char and ash from forest fires, which speculates that worms might have played an essential role in the formation of Terra preta. One of the unique aspects of Terra preta is how deeply integrated the char particles are in the soil matrix, and how small they are, visible only under a microscope, largely bound to clay particles via a calcium cation bridge.
Reducing the particle size increases the available surface area of the char. Fertility effects largely depend on exposed surface area. Reducing the particle size by half will double the exposed surface area. Imagine a cube of char 2 cm in each dimension. 6 faces of with an area of 4 cm2 each totals 24 cm2 of surface area. Break that cube down to precisely half its size, and you get 8 cubes 1 cm in each dimension. Each of the smaller cubes has a surface area of 6 cm2. 8 cubes x 6 cm2 = 48 cm2.
Crushing biochar to the size of sand particles is as effective as adding significantly more biochar of a larger particle size to a plot, so it is well worth the time. Starting with one 2 cm cube, reducing the size to 1 cm provides 48 cm2 surface area, 5 mm / 98 cm2, 2.5 mm / 196 cm2, 1.25 mm = 392 cm2, 0.6 mm = 800 cm2 surface area. 0.6 mm char particles will have 16 times more exposed surface area compared to the same amount, by weight of 1 cm char particles. Once they pass through a worm a few times, they will be even smaller.
All this crushing and vermicomposting takes time, but given that however you obtain it, biochar is expensive, I'd rather take the time to multiply the value of the biochar I can make or buy, than rush ahead to get it in the soil as soon as possible.