The eStore and eMember plugins are pre-integrated so using a WP eStore button to accept payment for membership is very easy.
The only thing you need to do is specify the “Membership Level ID” in the eStore product’s “Reference Text” field when you create/configure an “Add to Cart”, “Buy Now” or “Subscribe” button using eStore. This basically tells eStore which membership level a button corresponds to. You can create as many eStore payment buttons as you want for your different membership levels.
Buy Now Type Button or Subscription Type Button?

Difference between “Buy …

You can manage the protection of specific posts, pages, categories, comments from the “Manage Content Protection” menu of the eMember plugin. You can also set protection of a post or page while editing it in the WordPress editor.
Quick Summary of Content Protection
You perform the following operations in the “Manage Content Protection” menu to protect content in eMember.

Lock-down the content you want to protect via General Protection. Select the items you want protected.
Then select a membership level and select items you want accessible to that membership level. Do this step for all the …

WP eMember uses a concept of membership level. This is designed to give you (the site owner) the ability to easily control and assign what content your members can and cannot see on your site.
When a visitor becomes a member, he/she is assigned to one of the membership levels you created. The member will then have access to the site’s content based on the permissions you defined in the membership level.
Creating a Membership Level
To add a Membership Level you need to browse to the “Membership Level” menu.
From the “Manage Levels” …

The first thing you need to do after you activate the WP eMember plugin is head over to the settings menu page to configure some settings. Most of the settings fields are self explanatory and have help text next to it.
It is a good idea to read the Typical Membership Registration process documentation before you start setting up WP eMember.
The settings/options menu for the WordPress eMember Plugin can be found on the left hand side of your wordpress dashboard similar to the following screenshot (on WordPress version 2.7 or above)