Hi Mary. You can link to the headings and subheadings you have created with = signs on the free-space profile. For example, this link should work:
[[Space:Source_Documents_for_Bakker_ancestry#Meeden|Meeden marriage contract]]
The format is
[[SpaceID#heading|anchor]]
There are double square brackets around. SpaceID is the WikiTree ID of the free-space profile. Next is a # character, followed by the heading (if the heading contains spaces I think you may be able to leave them as is, or else replace them by underscores). Next is a | character, the so-called pipe character. Finally is the "anchor", whatever text you want displayed for the link.
Please try it out and reply if there are any issues.