Secure the bit about an 1/8" before the cutting edge starts. Tight, but not too extreme or you'll "spring" your collet. Adjust the base until you have (insert depth of cut here) of the cutting edge exposed.
So if you want your depth of cut to be 1/8", you should only have 1/8" of cut edge sticking out from the base.
Now get a scrap piece of wood, clamp it down so it is secure, put on your safety glasses and practice practice practice.... then practice some more. Preferably on a piece of pine or other soft wood so as to preserve the life of your cutting edge. Don't practice on MDF, it is extremely hard on your carbide and will dull your tool much quicker. Heat is the #1 enemy of your tool. Heat is dispersed through the chips that your tool creates, this is called your chipload. If you do not have a good chipload, your tool (bit) will heat up and that is what causes it to dull. You just can't get as good of a chipload on MDF as you can on solid woods. The grade of carbide on an off the shelf straight plunge router bit is not ideal for MDF. Sure it will work just fine, but it will dull much quicker than it would on a solid wood.
Make sure you wear those safety glasses.
Feel free to ask any questions you have. I work for a company that sells, services, and manufactures industrial woodworking tools.