First you must construc altar. This altar can be anything from milk crakes to a desk. Specially made ones from occult soe a lso be purchased. Also a pentagram on the floor works well enough.
Now that you have something like an altar you need to make it holy. You can add heads and skulls nimals and such and also draw on lots of nifty sybols. The last step is to make a sacrifice on t ml nimals and children work best at first. Then you should start getting into dogs and 3rd grdes.Cas ndchicklens also work. Remember: Anything less might do more bad then good!
Also music can be used to set the atmosphere. Loud and fast work work as well. Try slow and powerr praying to. Bands like Godflesh and Floyd. Loud fast stuff is good for your spare time. Recomeddbns are Morbid Angel and Diecide. Drugs can also better the experience.
If you parents or many visitors that you don't want to know about this llittle thing of yours, th might need other stuff. Sheets work to cover up small altars or pentagrams. Rugs can also be pto los to hide ones there. Also small more portable altars are good. You don't want to move it oomuh aye ven forcing the altar unholy. Just one you can put in the closet or something.