The objective is to catalogue all the processes / activities that use personal data. The GDPRWise App nicely groups processes into 3 sections: your Customer dossier, your Staff dossier and your Third Parties / suppliers dossier.
GDPR wants you to have a full picture of all processing activities that touch on personal data and then reflect on their relevance, security arrangements, risks etc. so you can improve where needed and communicate your privacy stance to all involved parties.
Based on the sector you operate in, the GDPRWise App suggests processes your firm is most likely running and which personal data items are most likely involved in those. For example your firm invoices customers and as a result captures some personal data on those customers while at the same time sharing some of that data with your accountant. Review & confirm the processes the App is suggesting for you and add others as needed.
There is no need to do all of the cataloguing in one go. Why not work section by section and let things sink in to come back and progress on a subsequent day. A lot of your activities are likely to be supported by software, so have those software apps open to confirm what personal data is being captured and potentially shared.