How many times do you water the plant aloe vera?

Depending on the size of the cactus, the pot it is in and the environment it is in, no more than once a week, and then a very small amount.

For example - Several small, decorative cacti planted, in well drained cactus mix, in an unglazed, flattish, terracotta dish need water every other week when indoors, if you set the same dish out of doors in a sunny but covered area (where no rain falls on it) you need to water it once a week. If rain falls on it, be very careful not to water it at all unless you have no rain for a month.

If your cactus is planted out doors, in the ground, you may not need to water it at all. A well established cactus can survive years in the desert with only what water it gets naturally.

Cacti are more susceptible to over-watering than under-watering. Always check the soil to be sure it is dry before adding water.