The same way anyone does, just not with each other. It takes one man (for the sperm) and one woman (for the egg) to make a baby, so the same-sex couples can not do this without a member of the opposite sex to help, or by adoption.
Some of the ways gay men have babies:
- If they are fertile and capable of making a baby, gay men can donate their sperm to a couple who want a baby (usually through artificial insemination. The couple can be a lesbian couple or heterosexual couple who are infertile).
- Some gay couples may use the sperm of one or the other man to have a surrogate mother impregnated, or if they cannot use their own sperm, they may have a surrogate mother use donated sperm to conceive the baby.
- Sometimes they adopt a baby to love.
Some of the ways lesbian women have babies:
- If one of the women is fertile and capable of making a baby, they can use the sperm of a donor male (either one they know or from a sperm bank), and their egg to have a baby themselves. This can be by artificial insemination or by natural sex if they have a male to help.
- If they are not capable of having the baby themselves, they can also use a surrogate mother.
- Sometimes they adopt a baby to love.
See the related questions for more information.