You want to increase your bioload? Add more fish or feed more often. Just about anything to dirty up the water.
Now I think what you ment to ask was this. How do I increase my bioload capacity. Allowing your system to support more fish, etc. Well the best way is to get a larger tank. Another way is to use a large sump to increase your total water capacity of the system. For example if you have a 55 and you get a 30 gal
sump your total effective water capacity will go up to approx 75 gal
or so. Now doing this does not enhance the filtration capacity so to do that you would need more live rock in the sump for additional bio filtration. A larger, oversized, skimmer will also improve water qulity to allow for more of a bio load.
Its important to note that having even a huge water capacity does not make up for having a small display tank. For example if you put another 55 gal
tank in as a sump your effective water capacity would be around 100 gal
but your display tank would still only be the size of a 55 gal
tank and overcrowding of fish can be just as detrmental as having to much of a bioload on the system.