SimConnect for external Addons

Hello volks,
i recently got started with the whole msfs setup and prepared myself a bunch of useful external addons and mods like certain replay tools or the landing rate application and so on. Sadly i cant get them to work. whenever i wanna use them i get a sim connect (missing/not found) whatever error or they simply wont connect and cant be used.
I was looking through several threads and topics, but i cant really find a solution working for me :(((((
maybe someone can help me with that? i heard it might has something to do with the dev mode sdk in msfs? if so how to get it, install it, i really dont get it. Its really sad using the sim without these modifications.

thanks in advance and happy landings