This can be completed by logging into WordPress. You will need to change the address in every section of the website where it is displayed. Generally, this is on the Contact Us page, sidebars, footers, and possibly the job board.
To change an address in a sidebar or in the footer: go to Appearance>Widgets and find the appropriate sidebar and/or footer. You will then click on the "Text" box and edit the current address. If you have a link to Google Maps, make sure you insert the one for the new address as well. You will then need to click the blue "Save" button underneath the text.
To change the address on your contact page: go to Pages in WordPress and then find the "Contact Us" page (or possibly the "Location" page, depending on what it is titled on your website). Once there, go to the text view and edit the current address to reflect the changes. Then press the "Update" button in the top right.
To change the address on mobile: Most addresses are located in the footer on mobile. In order to change the address on mobile, you will need to go to WPTouch Pro in WordPress, then Customize Theme and click on "Go to the customizer." You will then need to select the Footer and make edits. Once you have done this, make sure to click the blue "Save & Publish" button.
If your website does not have WPTouch Pro, then the Mobile header/footer will be located as a sidebar under Appearance>Widgets and will need to be edited like the sidebars mentioned above.
Finally, if the address is also located on the header or footer of the job board, and you have already changed the header or footer to reflect this change, you will need to add /?reload=1 at the end of the URL. For example: jobs.COMPANYNAME.com/?reload=1