To contact the person who entered data related to your ancestry, on the Profile page of an ancestor, under the profile information on the left side, you will see a line like this:
Profile manager: ___________ [send private message]
If you click on [send a private message] you can email the profile manager directly and share your information. You can also ask that profile manager to be invite you to be a member, and/or add you to their Trusted List(s). This will grant you access to both that ancestor profile and to WikiTree.
You might want to first search the Surname lists for Armstrong and/or Martin to see which profile manager has the majority on ancestor profiles that match your ancestors.
WikiTree is by invitation - you can also review the following page and see the Request an Invitation section, however, that will not connect you directly with an ancestor so you might want to try the above method first.