Just as with someone who is circumcised, you should always wait until the penis is fully erect and ready for sexual activity before attempting to put on the condom. If you try to put a condom on a non-erect penis, it can result in the condom sliding up, down, or off the penis. Place a small drop of water-based lubricant on the inside of the condom in the reservoir tip before you unroll it. Water-based lubricant can make it easier for you or your partner to roll the condom onto the penis. It can also increase the sensations he feels during sex.  Make sure you put just a small amount of lube in the reservoir tip. Using more lube could take up too much space in the reservoir tip, and leave little to no room for semen. Use water-based lube only. An oil-based lube can damage the latex condom, and increase the risk for pregnancy and the transmission of STDs. Before you put the condom on, gently pull back the foreskin. Pull it back until the head of the penis is fully exposed. Remember this is a very sensitive area, so be extra gentle. Pulling back the foreskin will make it easier for you to get the condom on properly.  Generally the foreskin will remain securely retracted one you have rolled it down off the head of the penis. If it rolls back up again before you get the condom, just roll it down and try again.

How would you rephrase that briefly using Chinese?
等阴茎完全勃起时再戴套。 加滴润滑液。 撸下包皮。