If you would like commissions added when members recruit other members, go to the Setup->Program Settings menu to define your compensation plan. The bottom section on this page allows you to create new commission transactions, and looks like:

This small forms asks for the commission type and member type for the new commission transaction. Sign Up commissions are added immediately after a new member joins and pays their membership fee, while recurring commissions are added after a member has paid their recurring (eg. monthly) membership fee. The member type allows you to specify which member type must join and pay their membership fee in order for this commission to be added.
Using the above example, the commission will be added to the member's sponsor every time a Gold member joins. The next page shown after you submit the form allows you to define the exact commission amounts that will be added. This page will look something like:

The table contains one column for each member type in the database, and one row for each needed downline level. The commission amounts you specify in this table will be added to the sponsor / upline, depending on the member type the sponsor is. Using the above example, every time a new Gold member joins, if their sponsor is a Basic member they will receive $3 in commission, and if their sponsor is a Gold member they will receive $5 in commission.
Continue the above process until you have created all needed commission transactions for your online business.