Welcome to the Moodle community, Sarah
There are several ways to achieve this (all helped by the open source nature of Moodle) and depends exactly what you want to achieve.
1. Look at the functionality you want and firstly ensure it isn't already in Moodle core or covered by plugins that already exist and can be installed as they are, or achieved by good instructional design
2. An in-house developer to tweak and customise existing code/plugins to meet specific needs - or simply an admin to make use of settings pages, especially around some of the theme designs
3. If custom development is needed then
a. in-house (depends on skills/time/capacity)
b. Moodle partner https://moodle.com/partners/?mode=search&services=support
c. Put an advert on the Moodle jobs page for a contractor for a specific project https://moodle.org/mod/data/view.php?id=7232
Of course, any and all of these options are supported by the wonderful community here in the forums
Richard
PS. Just as a side note, the forum you have posted in is actually a forum about using the forums activity within Moodle, one of the moderators might move this for you into a more appropriate forum (possibly General Help) simply because being in the appropriate forum helps get the right people supporting you