To start caulking your shower please ensure that the shower is clean, dry and all caulk joints are also clean, dry and free of any old caulk. Start by taping the 'to be caulked' areas with blue painters tape, making sure you are following the contour of the shower and pressing firmly on the tape to prevent any caulk from getting under the tape. Once the taping is completed now you can start caulking. Start by using a caulking gun from one end of the shower to another, using small amounts of caulk avoiding any gaps in caulk. Once this is done, use a wet finger to smooth the caulk down from one end to another using a smooth fluid motion. After this you can now remove the painters tape. Start by pulling tape away from the caulked area so you do no disturb the wet caulk. This step can be messy so be careful, always making sure you are pulling the tape away from the caulk. Once you have pulled all the tape off, now just let the caulk dry and you are done!