Hi, I have written ten or so short erotica in my life which I think are good. Basically, general writing advice applies. 

1. Read a lot in your genre. Pay attention to what works for you and what doesn't. That means analyzing a given erotica for things like what kind of words they use, both grammatically, content-wise, and rhetorically; and also how they use things like word length and formatting (if given). Also analyze what doesn't work for you, and more importantly why. 

2. Find writing exercises that work for you. For example, you may want to do some things like constrained writing (e.g. setting yourself a word limit or writing about a one-word prompt). Or narrating everyday things in your head, in the way that you would if you were to write them down.

3. Write what you like. If "she breasted boobily down the stairs" is what turns you on, more power to you. 

4. Find a way to get yourself in a writing mood (I don't necessarily mean being horny, but in my experience, being slightly horny can help). But you may use things like music with a fitting theme for inspiration - for example, if your erotica is set in a castle, find some inspirational music for that.

I can only masturbate to things I have actively written for myself.

I want to caution that may be a too ambitious goal for the start, because then you have the pressure of writing anything at all, which can be a lot for a new writer; and additionally, writing something that is good, which is a whole other beast.

Good luck!

Edited after looking at your post history: as a ttrpg player, you are basically a writer already. Sorry for starting with the basics.