I'm not an Alocet employee, but as a fellow user I can give you some pointers:
The Tables screen in the Customize tab shows you a list of tables, and if you edit those tables you can view/add fields. However, you cannot add or edit records for the table from that screen.
(This applies to you because you presumably want to add more options to the LeadStatus dropdown.)
Lets say you want to add more records to a simple dropdown table like the LeadStatus table. This table has only one field, the LeadStatus field. The easiest way to do this is to create a simple screen for the sole purpose of adding records:
1. Go to the Screens screen in the Customize tab, and enter your new screen name and click continue.
2. Follow the steps, choosing a tab to display your screen in, etc. At some point it will ask you to choose a table to base your new screen off of. Choose the LeadStatus table.
3. Now you can edit your new screen. Add a grid object (this object provides a convenient spreadsheet-like visual used to access data in your tables), then edit that grid object.
4. In the edit grid options, set it to be based on the LeadStatus table. One of the editing screens is for inserting fields from the table that you want displayed as columns in the grid. Since there is only one field in the table, add the LeadStatus field as a column. (You may also notice the RecordID field, which is one that all tables have by default and is the uneditable and unique key for the records in the table; it's not necessary here).
Other options you'll want to enable when editing the grid is to allow yourself to both edit and add entries within the grid.
5. Save and publish your new screen. Now when you go to the screen in Method, you should see a grid that lists all the records from the LeadStatus table, and it should also let you edit the existing records or add new ones, like "Initial", "Contact & Qualify", etc. (Note: deleting records from the table involves a couple more steps and using some Method Actions, so I'll hold off until you need that)