There is no specific procedure for asking asylum on the basis of sexual orientation or gender identity.
Fedasil info is the official information platform for asylum seekers in Belgium. There you will find information about the asylum procedure, among other things. The website is only available in Belgium. You will find information in twelve languages: Dutch, French, English, Arabic, Farsi, Pashtu, Russian, Spanish, Albanian, Turkish, Somali and Tigrinya. Eight of these languages also have an audio version.
The website AsylumInfo.be is currently (October 2019) working on an update. Not all information on the multilingual website is currently up-to-date.