You can see a list of all groups in your project by scrolling to the bottom of the project browser to the Groups category. Click the + button to see the subcategories Model groups and Detail groups. Then click the + button next to whichever subcategory you put the lines (if they are detail lines they will be under Detail, if model lines they will be under Model). These lists show the names of all of your groups, thus the importance of naming them. It is quite annoying to have a list which merely shows you "Group 1," "Group 2," and so on when all the groups are quite different from each other.
To place one of these groups, click the + button on the group you wish to place, then select that group's Type (a Type will not have a + button next to it; in other words, you cannot drill down further into a type in the project browser). Then right-click and select Create Instance.
The button on the ribbon works well too, but my opinion is that it is easier to see all the groups in the project by using the project browser.
