When you go into a sunbed for the first time you should only lay in the sunbed for up to 6 minutes.
Go twice per week and do a 6 minute tanning session each of those days for the first month or so.
Then after that you can increase your tanning sessions to 10 to 12 minutes but I would not recommend going any longer than 12 minutes at a time in a sunbed.
The more time you spend in the sunbed or tanning bed the more you increase your chances of developing skin cancer.
Never go more than a few times in a week and skip a few days before going tanning in the sunbed again.
Going too often to the sunbed also increases your chance of developing cancer.
If you're under 35 you also have an increased risk of skin cancer from sunbeds so if you plan to use a sunbed it's best to wait until after 35 years old.