Place the new tube of silicone in the gun, and cut off about a half inch off of the tip. Poke the hole from the tip of the new silicone, with the accessory on the caulking gun.

Press slowly until the glue comes out slightly. Start from one end and press into the crack as you run the silicone to the other end in one motion. Use an amount of glue so that it comes out slightly at the corners that you're caulking.

Make sure to put enough glue and not too little, as you will need to run your finger down the glue in one motion to smooth it out. Run your finger only once.

Wait about 10 minutes and remove the tape, so that the glue doesn't fully dry with the tape. The finish will also look cleaner when you remove the tape after caulking.