Unless you're trying to mask your identity from your ISP, instance or government, I don't really see how tor is useful here, given that you're presumably posting on the clearweb anyway.
It's hard to give specific useful advice, because you're so vague about what you're trying to post, and who you want anonymity from. If it's just other users on lemmy, don't bother using tor, just create a burner account and access it normally via the web.
Unsurprisingly, instances aren't super keen on letting users access their platform via tor since it's an effective method of ban evasion, and thus people will mostly be using it to post awful things they didn't want in the first place.