I do not know SynFull. but it is a VST2 we support it. We do not support VST3.
You can see how to use VST2 instruments and effects in this video
If you need general help with LMMS try Rookie-guide in signature
Let us know if you got the issues fixed or need more assistance.
Besides that, since you are new in Forum
Welcome HotRats!
Here are all important links:
http://lmms.io/forum/viewtopic.php?f=1&t=4740
-A few rules and useful forum instructions
If you like to introduce yourself, to the community, go here:
http://lmms.io/forum/viewtopic.php?f=4&t=4480