First of all, the black pipe is ABS. The white parts you bought are PVC. ABS and PVC are chemically different and can not be intermixed. Since your existing pipe is ABS, you need ABS parts. Secondly, you do not use silicone to join the parts. ABS and PVC are solvent welded, but since they different materials the each require their own solvent. These solvents are commonly but incorrectly referred to as glue, but because they actually melt the surfaces of the pipe and fittings briefly so that when the parts are slipped together, the two surfaces combine as a chemical weld. ABS requires ABS solvent and PVC requires PVC solvent.