When and how should I cut the leaves to keep the plant he...
1
Wherever you cut off an aloe leaf to use, it will just scab over. Be sure to use a very sharp pair of scissors or pruners that have been sanitized with 70% or higher isopropyl alcohol, which minimizes the risk of disease entering the plant through the cut.
Personally, I would wait until your aloe plant is larger and more mature before harvesting leaves. It's still quite small, so removing leaves now could cause it to go into shock. Also, you'll want to move it into a proper pot with drainage holes at the bottom. Drainage holes are essential for plant health...they help the soil dry out faster and also allow excess fertilizer and mineral buildup to be flushed out. Aloe can easily rot if left in damp soil, so a set up that allows the soil to dry out as quickly as possible is ideal. That's why terracotta pot are recommended for aloe and other succulents—they're porous, which improves airflow to the soil and helps it dry out faster. Aloe also prefers a gritty, well-draining soil. Something like succulent/cacti soil mixed with equal parts perlite or pumice is a good choice.
Personally, I would wait until your aloe plant is larger and more mature before harvesting leaves. It's still quite small, so removing leaves now could cause it to go into shock. Also, you'll want to move it into a proper pot with drainage holes at the bottom. Drainage holes are essential for plant health...they help the soil dry out faster and also allow excess fertilizer and mineral buildup to be flushed out. Aloe can easily rot if left in damp soil, so a set up that allows the soil to dry out as quickly as possible is ideal. That's why terracotta pot are recommended for aloe and other succulents—they're porous, which improves airflow to the soil and helps it dry out faster. Aloe also prefers a gritty, well-draining soil. Something like succulent/cacti soil mixed with equal parts perlite or pumice is a good choice.