Just follow the download link and everything is set.
At this time, we only support Android, iOS and Desktop browser.

You don't. However phonenumber help your friends can easily reach you, and if there are any problems with social network account (Google, Facebook), the linked phonenumber will come to the rescue.
In the future, we will profile inter-group features which work only if your account is linked with phonenumber.

You need invite link from the Admin to join a group, just click it then you can send your request. You will be the member right after the Admin accepts your request.
There is another way is Admin searches and adds your account manually using phonenumber or email. In this case, you need to confirm joining group by click Action Menu (button "⋮" on upper right) from Homepage then choose Invitations.
If there are no groups, you may want to create a new one and become the Admin. Details below.

Easy as pie to create a new group by anyone.
From Homepage, click Action menu (button "⋮" on upper right) >> Create new group. In put Group name and Description by your derise, then create the first Fund of group. You can also create more Funds later, and of cause, you'll be the person in charge of all Funds.

Being the Admin, the simplest way is sending Invite link to members through IM applications such as Zalo, Whatsapp, Viber, ... Go to Action menu of Group, click "Edit group" then you can copy the Link. Just make sure that Invite link is on.
Whenever a new member requests to join you will receive a notification and it needs your approval to become a member.